Semiconductor device

ABSTRACT

It is an object of the present invention to provide a technique in which a high-performance and high reliable memory device and a semi-conductor device provided with the memory device are manufactured at low cost with high yield. The semiconductor device includes an organic compound layer including an insulator over a first conductive layer and a second conductive layer over the organic compound layer including an insulator. Further, the semiconductor device is manufactured by forming a first conductive layer, discharging a composition of an insulator and an organic compound over the first conductive layer to form an organic compound layer including an insulator, and forming a second conductive layer over the organic compound layer including an insulator.

TECHNICAL FIELD

The present invention relates to a semiconductor device and a method formanufacturing a semiconductor device.

BACKGROUND ART

In recent years, individual recognition technology has attractedattention. For example, there is a technology to be used for productionand management, in which information such as a history of the object isclarified by giving an ID (an individual recognition code) to anindividual object. Above all, the developments of semiconductor devicesthat can send and receive data without contact have been advanced. Assuch semiconductor devices, in particular, an RFID (Radio FrequencyIdentification) (also referred to as an ID tag, an IC tag, and IC chip,an RF (Radio Frequency) tag, a wireless tag, an electronic tag) isbeginning to be introduced into companies, markets, and the like.

Many of the semiconductor devices have a circuit using a semiconductorsubstrate such as silicon (Si) substrate (hereinafter, also referred toas an IC (Integrated Circuit) chip) and an antenna, and the IC chipincludes a memory circuit (hereinafter, also referred to as a memory)and a control circuit. Further, an organic thin film transistor(hereinafter, also referred to as a TFT) using an organic compound forthe control circuit and a memory circuit has been actively developed(for example, Patent Document 1).

Japanese Patent Application Laid-Open No. H7-22669

DISCLOSURE OF INVENTION

However, in the case of a memory circuit using an organic compound thatis provided between a pair of electrodes to form a memory element, thereare following problems depending on a size of the memory circuit: when afilm thickness of the organic compound layer is thick, a writing voltageincreases. Alternatively, when a size of an element is small and athickness of the organic compound layer is thin, variation incharacteristics of a memory (a writing voltage and the like) is causedand normal writing can not be performed because the organic compound isto be easily affected by dust and an unevenness shape of a surface of anelectrode layer.

Therefore, it is an object of the present invention to provide atechnique in which a memory device and a semiconductor device providedwith the memory device, each of which have high-performance and highreliability can be manufactured at low cost with high yield.

In the present invention, an organic compound including a plurality ofinsulators is formed, which is provided between a pair of conductivelayers forming a memory element in a semiconductor device. Theinsulators in the organic compound layer exist inside of the organiccompound layer and at the interfaces with the conductive layers. Theorganic compound layer including an insulator can control aconcentration of the insulators in the layer depending on a material anda forming method thereof. Therefore, the insulators may be dispersedevenly in the organic compound layer, and the insulators may bedispersed unevenly so that the concentration of the insulators in theorganic compound layer is to be different. A tunnel injection becomespossible due to the insulators at the interfaces of the conductivelayers and the organic compound layer, and then, a tunnel current flows.Therefore, by applying a voltage between a first conductive layer and asecond conductive layer, the current flows in the organic compound,which generates heat (Joule heat). Then, when a temperature of theorganic compound layer rises to a glass-transition temperature, amaterial forming the organic compound layer becomes a composition havingfluidity. The composition having fluidity flows without keeping a shapeof a solid state. Therefore, a film thickness of the organic compound isuneven due to an influence of Joule heat and high electric field, andthe organic compound layer is transformed. Then, a part of the firstconductive layer and the second conductive layer is in contact with eachother, and the memory element is short-circuited. Accordingly,conductivity of the memory element is changed before and after ofapplying the voltage.

Since an insulator does not transport carriers, a carrier transportingproperty of the entire organic compound layer is reduced due toobstruction of the insulator. Therefore, a current value that isnecessary for short-circuit (writing into a element) is reduced even inan organic compound material having a high carrier transportingproperty; thus an advantage such as low power consumption and expansionof selection range of a material is brought. Further, a mixed layerincluding an insulator hardly causes a defect due to crystallization ofan organic compound, and stabilizes a state of an organic compound layer(morphology) rather than a single layer of an organic compound.Therefore, manufacturing a defective element that is short-circuitedbetween conductive layers can be prevented in an initial state, andyield is improved.

It is to be noted that a semiconductor device in the presentspecification indicates a device capable of operating by utilizingsemiconductor characteristics. By using the present invention, anintegrated circuit having a multi-layer wiring and a semiconductordevice such as a processor chip can be manufactured.

One aspect of a semiconductor device of the present invention has amemory element, which includes an organic compound layer including aninsulator over a first conductive layer and a second conductive layerover the organic compound including layer an insulator.

The semiconductor device has a memory element that includes an organiccompound layer including an insulator over the first conductive layerand a second conductive layer over the organic compound layer includingan insulator. The organic compound layer including an insulator has aconcentration gradient of the insulator.

The concentration gradient of the insulator in the above organiccompound layer can be controlled as follows depending on a material anda manufacturing method. A semiconductor device in which a concentrationof the insulator in an organic compound layer at an interface of theorganic compound layer including an insulator and a first conductivelayer is higher than that at an interface of the organic compound layerincluding an insulator and a second conductive layer; a semiconductordevice in which a concentration of an insulator in an organic compoundlayer at an interface of the organic compound layer including aninsulator and a second conductive layer is higher that at an interfaceof the organic compound layer including an insulator and a firstconductive layer; a semiconductor device in which a concentration of aninsulator in an organic compound layer at an interface of the organiccompound including an insulator and a first conductive layer and at aninterface of the organic compound including an insulator and a secondconductive layer is highest in the organic compound including aninsulator; and the like can be manufactured.

In the present specification, a high concentration indicates a highexisting probability and a large quantity of distribution of aninsulator. These concentrations can be represented as a volume ratio, aweight ratio, a composition ratio, and the like by properties of matterof a material.

One aspect of a method for manufacturing a semiconductor device of thepresent invention includes the steps of forming a first conductivelayer, forming an organic compound layer including an insulator over thefirst conductive layer, and forming a second conductive layer over theorganic compound layer including an insulator to form a memory element.

Another aspect of a method for manufacturing a semiconductor deviceincludes the steps of forming a first conductive layer, discharging andsolidifying a composition including an insulator and an organic compoundover the first conductive layer to form an organic compound layerincluding an insulator, and forming a second conductive layer over theorganic compound layer including an insulator to form a memory element.

Another aspect of a method for manufacturing a semiconductor deviceincludes the steps of forming a first conductive layer, forming anorganic compound layer over the first conductive layer, adding aninsulator to the organic compound layer to form an organic compoundlayer including an insulator, and forming a second conductive layer overthe organic compound layer including an insulator to form a memoryelement.

In accordance with the present invention, a memory element and asemiconductor device, each of which has high-performance and highreliability, can be manufactured at low cost with high yield.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view describing the present invention;

FIGS. 2A to 2C are views describing a memory device of the presentinvention;

FIG. 3 is a diagram describing a memory device of the present invention;

FIGS. 4A and 4B are a diagram and a view describing a memory device ofthe present invention;

FIG. 5 is a diagram describing a memory device of the present invention;

FIG. 6 is a view describing a memory device of the present invention;

FIG. 7 is a view describing a memory device of the present invention;

FIGS. 8A and 8B are views describing a memory device of the presentinvention;

FIG. 9 is a diagram describing a memory device of the present invention;

FIG. 10 is a view describing a semiconductor device of the presentinvention;

FIG. 11 is a view describing a semiconductor device of the presentinvention;

FIGS. 12A and 12B are views describing a semiconductor device of thepresent invention;

FIGS. 13A to 13G are views describing application examples ofsemiconductor devices of the present invention;

FIGS. 14A and 14B are a graph and a diagram describing a memory elementof the present invention;

FIG. 15 is a view describing a droplet discharge device which isapplicable to the present invention;

FIGS. 16A to 16C are views describing a memory device of the presentinvention;

FIGS. 17A to 17C are views describing a memory device of the presentinvention;

FIGS. 18A to 18C are diagrams describing a memory device of the presentinvention;

FIGS. 19A to 19C are diagrams describing a memory device of the presentinvention;

FIGS. 20A to 20C are graphs of experimental data of comparativeexamples;

FIG. 21 is a sectional-photograph of a memory element of an comparativeexample;

FIG. 22 is a characteristic graph of a memory element in Embodiment 1;

FIGS. 23A and 23B are characteristic graphs of a memory element inEmbodiment 1;

FIG. 24 is a characteristic graph of a memory element in Embodiment 1;and

FIG. 25 is a characteristic graph of a memory element in Embodiment 1.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment modes of the present invention will be described in detailwith reference to the accompanying drawings. However, it is to be easilyunderstood that various changes and modifications will be apparent tothose skilled in the art, unless such changes and modifications departfrom the content and the scope of the invention. Therefore, the presentinvention is not construed as being limited to the description of thefollowing Embodiment modes. It is to be noted that the same portion or aportion having the same function is denoted by the same referencenumeral in all the drawings, and the description thereof is omitted.

Embodiment Mode 1

In the present embodiment mode, an example of a structure of a memoryelement included in a memory device of the present invention will bedescribed with reference to drawings.

A memory element of the present invention and an operating mechanismthereof are described with reference to FIG. 1. In the presentembodiment mode, an organic compound, which is provided by beinginterposed between a pair of conductive layers that forms a memoryelement included in a memory device, is formed so as to include aplurality of insulators. Then, the organic compound is made to be anorganic compound layer including a plurality of insulators. By having anorganic compound layer including an insulator, characteristics of amemory element is stabilized without variation, and normal writing canbe performed.

The insulators in the organic compound layer may be distributed evenlyor distributed unevenly so that the organic compound layer has aconcentration gradient of the insulators. Mixed condition of theinsulators in the organic compound layer is different depending on amaterial and a forming method, and the concentration can be controlled.

A memory element shown in FIG. 1 is an example of a memory element ofthe present invention, in which an organic compound layer 52 includingan insulator 51 a and an insulator 51 b is formed over a firstconductive layer 50, and a second conductive layer 53 is formed over theorganic compound layer 52.

As a material for the first conductive layer 50 and the secondconductive layer 53, an element, a compound, or the like having highconductivity is used. As a material for the organic compound layer 52 inthe present embodiment mode, a substance the crystallinity,conductivity, and a shape of which are changed by electric action isused. Since a memory element having the above structure has conductivitythat changes before and after of applying a voltage, the memory elementcan memorizes two values corresponding to “initial state” and “afterchange of conductivity”. The change in conductivity of the memoryelement before and after applying a voltage will be described.

In the present embodiment mode, the organic compound layer 52 includingthe insulator 51 a and the insulator 51 b, which forms a memory elementincluded in a memory device, is formed over the first conductive layer50. When a voltage is applied between the first conductive layer 50 andthe second conductive layer 53, a current flows to the organic compoundlayer 52 to generate heat. Then, when a temperature of the organiccompound layer 52 increases to a glass-transition temperature, amaterial forming the organic compound layer 52 becomes a compositionhaving fluidity. The composition having fluidity flows without keeping ashape of a solid state. Therefore, a film thickness of the organiccompound layer 52 becomes uneven due to an influence of Joule heat andhigh electric field, and the organic compound layer is transformed.Then, the first conductive layer 50 and the second conductive layer 53are connected with each other. As a result, the first conductive layer50 and the second conductive layer 53 are short-circuited. Therefore,the conductivity of the memory element is changed before and afterapplying a voltage.

A tunnel injection of carriers from the first conductive layer 50 to theorganic compound layer 52 becomes possible by the insulator 51 aexisting at an interface of the organic compound layer 52 and the firstconductive layer 50. Accordingly, characteristics of a writing voltageof a memory element and the like are stabilized without variation, andnormal writing in each element can be performed. Further, since aplurality of insulators is mixed in the organic compound layer,morphology of the organic compound layer is stabilized. Furthermore,since a carrier injection property is improved by the tunnel injection,a film thickness of the organic compound layer can be also increased.Therefore, a defect in which a memory element is short-circuited in theinitial state before having conductivity can be prevented.

Since the insulator 51 b existing in the organic compound layer 52 doesnot transport carriers, a carrier transporting property of the entireorganic compound layer 52 is reduced due to obstruction of the insulator51 b. Therefore, a current value that is necessary for short-circuit(writing into a element) is reduced even in a case of an organiccompound material having a high carrier transporting property; thus, anadvantage such as low power consumption and expansion of selection rangeof a material is brought.

FIG. 1 shows an example where the insulator 51 b, and the insulator 51 aexisting at the interface of the first conductive layer 50 are includedin the organic compound layer 52; however, the present invention is notlimited thereto as far as an insulator is included in an organiccompound. Therefore, both of the insulator 51 a and the insulator 51 bare not necessary to exist, and a structure in which either one existsmay be employed.

As a voltage that is applied to a memory element of the presentinvention, a voltage that is applied to a first conductive layer may behigher than a voltage that is applied to a second conductive layer.Alternatively, a voltage that is applied to the second conductive layermay be higher than a voltage that is applied to the first conductivelayer. In the case where a memory element has rectification, a potentialdifference may be provided between the first conductive layer and thesecond conductive layer so as to apply a voltage in the direction offorward bias. Alternatively, a potential difference may be providedbetween the first conductive layer and the second conductive layer so asto apply a voltage in the direction of reverse bias.

In the present invention, an organic compound layer including aplurality of insulators, which is provided between a pair of conductivelayers by mixing the plurality of insulators, is used. Mixed conditionof the plurality of insulators into the organic compound layer isdifferent depending on a material, a forming method, or the like. Theorganic compound layer including an insulator shown in FIG. 1 is anexample where the insulators are dispersed almost evenly in the organiccompound layer, and a concentration thereof is even. Insulators may bemixed evenly in an organic compound layer as FIG. 1; alternatively,insulators may be mixed unevenly so that the organic compound layer hasa concentration gradient of the insulators. An example of mixedcondition of insulators in an organic compound layer is described withreference to FIGS. 16A to 16C.

A memory element shown in FIG. 16A is an example of a memory element ofthe present invention, in which an organic compound layer 62 includingan insulator mixed region 61 is formed over a first conductive layer 60,and a second conductive layer 63 is formed over the organic compoundlayer 62. The organic compound layer 62 has a concentration gradient ofinsulators mixed therein, and the insulators exist unevenly in theorganic compound layer 62. The insulator mixed region 61 is formed inthe vicinity of an interface of the organic compound layer 62 and thefirst conductive layer 60. Accordingly, in the organic compound layer62, a concentration of the insulators at the interface of the organiccompound layer 62 and the first conductive layer 60 is highest in theorganic compound layer 62. The insulator mixed region does not have aclear interface with a non-insulator mixed region. Accordingly, theinsulator mixed region can have a structure in which a concentration ofthe insulators is changed gradually as approaching the second conductivelayer 63 in the direction of the film thickness in the organic compoundlayer.

A memory element shown in FIG. 16B is an example of a memory element ofthe present invention, in which an organic compound layer 72 includingan insulator mixed region 71 is formed over a first conductive layer 70,and a second conductive layer 73 is formed over the organic compoundlayer 72. The organic compound layer 72 has a concentration gradient ofinsulators mixed therein, and the insulators exist unevenly in theorganic compound layer 72. The insulator mixed layer 71 is formed in thevicinity of an interface of the organic compound layer 72 and the secondconductive layer 73. Therefore, a concentration of the insulators at theinterface of the organic compound layer 72 and the second conductivelayer 73 is highest in the organic compound layer 72. The insulatormixed region does not have a clear interface with a non-insulator mixedlayer. Accordingly, the insulator mixed region can have a structure inwhich a concentration of the insulators is changed gradually asapproaching the second conductive layer 73 in the direction of the filmthickness.

A memory element shown in FIG. 16C is an example of a memory element ofthe present invention, in which an organic compound layer 82 includingan insulator mixed region 81 a and an insulator mixed region 81 b isformed over a first conductive layer 80, and a second conductive layer83 is formed over the organic compound layer 82. The organic compoundlayer 82 has a concentration gradient of insulators mixed therein, andthe insulators exist unevenly in the organic compound layer 82. In theorganic compound layer 82, the insulator mixed region 81 a is formed inthe vicinity of an interface with the first conductive layer 80, and theinsulator mixed layer 81 b is formed in the vicinity of an interfacewith the second conductive layer 83. Therefore, a concentration of theinsulators at the interface of the organic compound layer 82 and thefirst conductive layer 80 and at the interface of the organic compoundlayer 82 and the second conductive layer 83 is highest in the organiccompound layer 82. The insulator mixed region does not have a clearinterface with a non-insulator mixed region; accordingly, aconcentration of the insulators is changed gradually. The organiccompound layer 82 can have a structure in which the concentration of theinsulators becomes higher as approaching the first conductive layer 80and the second conductive layer 83 in the direction of the filmthickness direction; and the insulators is included at a lowconcentration in the middle part.

An organic compound including a plurality of insulators may be formed inone process by mixing a plurality of insulators and an organic compound.Alternatively, either one may be formed in advance to introduce (add)the other in another process. In a case of forming the organic compoundlayer including a plurality of insulators in one process, a dry processsuch as a co-evaporation method and sputtering may be employed. Inaddition, a mixed material of a plurality of insulators and an organiccompound may be used to form the organic compound layer including aplurality of insulators into a film by a wet process such as a coatingmethod. The insulators in the organic compound layer are distributed sothat a concentration of the insulators can be controlled to be apredetermined concentration by using the above forming method.

In the case of wet type, the insulators and the organic compound may bedissolved in a solvent, and even if insoluble, they may be dispersed tobe mixed. Therefore, a colloid solution in which a plurality ofinsulators are in fine particles of approximately 0.1 μm to 0.001 μm(also referred to as colloid particles) to be dispersed in liquid can beused. The materials may have any shapes such as particle shape, columnarshape, needle shape, or planar shape. Further, the insulators may beaggregated to form an aggregation. A layer having a concentrationgradient may be formed due to a difference of specific gravity andsolubility between the insulators and the organic compound. For example,a concentration of the insulators at the vicinity of the interface ofthe organic compound layer and the conductive layer can be controlled byan insulator concentration that is capable of causing a tunnelinjection. Alternatively, a concentration of the insulators inside ofthe organic compound layer can be controlled by an insulatorconcentration that can save a carrier transporting property necessaryfor a memory element. By forming an organic compound layer including aninsulator in one process in such a manner, the number of processes canbe simplified.

The organic compound including an insulator can be formed by using anevaporation method such as an electron beam evaporation method and aco-evaporation method; sputtering, a CVD method; a coating method suchas a spin coat method using a mixed solution; and a sol-gel method. Theorganic compound layer including an insulator can be formed bydepositing each material concurrently by combining the same or differentmethods such as a co-evaporation method of resistance heatingevaporation, a co-evaporation method of electron beam evaporation, aco-evaporation method of resistance heating evaporation and electronbeam evaporation, deposition of resistance heating evaporation andsputtering, and deposition of electron beam evaporation and sputtering.Further, a droplet discharging (jetting) method (also referred to as aninkjet method depending on its system) in which a droplet of a compoundblended for a specific purpose can be discharged (jetted) selectively toform a predetermined shape; a dispenser method; a method in which anobject can be transferred or described into a predetermined shape, forexample, various printing methods (a method for forming an object into apredetermined shape such as screen (mimegraph) printing, offset(planography) printing, relief printing, and gravure (intaglio)printing); and the like can be also used. Furthermore, instead offorming the organic compound layer including an insulator concurrently,after forming an organic compound layer, insulators may be introduced byan ion injecting method, a doping method, or the like to form a mixedlayer of the insulator and the organic compound.

In the present invention, as for an insulator to be mixed into anorganic compound layer, a thermally and chemically stable inorganicinsulator or organic compound in which carriers are not injected areused. An insulator mixed into an organic compound layer in whichelectric conductivity is 10⁻¹⁰ s/m or less can be preferably used, andmore preferably, an insulator mixed into an organic compound layer inwhich electric conductivity is 10⁻¹⁰ s/m or more and 10⁻¹⁴ s/m or lesscan be used. Specific examples of an inorganic insulator and an organiccompound that can be used for an insulator will be described below.

In the present invention, as an inorganic insulator that can be used foran insulator mixed into an organic compound layer, an oxide such aslithium oxide (Li₂O), sodium oxide (Na₂O), potassium oxide (K₂O)rubidium oxide (Rb₂O), beryllium oxide (BeO), magnesium oxide (MgO),calcium oxide (CaO), strontium oxide (SrO), barium oxide (BaO), scandiumoxide (Sc₂O₃), zirconium oxide (ZrO₂), hafnium oxide (HfO₂),rutherfordium oxide (RfO₂), tantalum oxide (TaO), technetium oxide(TcO), ion oxide (Fe₂O₃), cobalt oxide (CoO), palladium oxide (PdO),silver oxide (Ag₂O), aluminum oxide (Al₂O₃), gallium oxide (Ga₂O₃), orbismuth oxide (Bi₂O₃) can be used.

In the present invention, as another inorganic insulator that can beused for an insulator mixed into an organic compound layer, a fluoridesuch as lithium fluoride (LiF), sodium fluoride (NaF), potassiumfluoride (KF), rubidium fluoride (RbF), beryllium fluoride (BeF₂),magnesium fluoride (MgF₂), calcium fluoride (CaF₂), strontium fluoride(SrF₂), barium fluoride (BaF₂), aluminum fluoride (AlF₃), nitrogentrifluoride (NF3), sulfur hexafluoride (SF₆), silver fluoride (AgF), ormanganese fluoride MnF₃ can be used.

In the present invention, as another inorganic insulator that can beused for an insulator mixed into an organic compound layer, a chloridesuch as lithium chloride (LiCl), sodium chloride (NaCl), potassiumchloride (KCl), beryllium chloride (BeCl₂), calcium chloride (CaCl₂),barium chloride (BaCl₂), aluminum chloride (AlCl₃), silicon chloride(SiCl₄), germanium chloride (GeCl₄), tin chloride (SnCl₄), silverchloride (AgCl), zinic chloride (ZnCl), titanium tetrachloride (TiCl₄),titanium trichloride (TiCl₃), zirconium chloride (ZrCl₄), iron chloride(FeCl₃), palladium chloride (PdCl₂), antimony (III) chloride (SbCl₃),antimony chloride (SbCl₂), strontium chloride (SrCl₂), thallium chloride(TlCl), copper chloride (CuCl), manganese chloride (MnCl₂), or rutheniumchloride (RuCl₂) can be used.

In the present invention, as another inorganic insulator that can beused for an insulator mixed into an organic compound layer, a bromidesuch as potassium bromide (KBr), cesium bromide (CsBr), silver bromide(AgBr), barium bromide (BaBr), silicon bromide (SiBr₄), or lithiumbromide (LiBr) can be used.

In the present invention, as another inorganic insulator that can beused for an insulator mixed into an organic compound layer, an iodidesuch as sodium iodide (NaI), potassium iodide (KI), barium iodide(BaI₂), thallium iodide (TlI), silver iodide (AgI), titanium iodide(TiI₄), calcium iodide (CaI₂), silicon iodide (SiL₄), or cesium iodide(CsI) can be used.

In the present invention, as another inorganic insulator that can beused for an insulator mixed into an organic compound layer, a carbonatesuch as lithium carbonate (Li₂CO₃), potassium carbonate (K₂CO₃), sodiumcarbonate (Na₂CO₃), magnesium carbonate (MgCO₃), calcium carbonate(Ca₂CO₃), strontium carbonate (SrCO₃), barium carbonate (BaCO₃),manganese carbonate (MnCO₃), iron carbonate (FeCO₃), cobalt carbonate(COCO₃), nickel carbonate (NiCO₃), copper carbonate (CuCO₃), silvercarbonate (Ag₂CO₃), or zinc carbonate (ZnCO₃) can be used.

In the present invention, as another inorganic insulator that can beused for an insulator mixed in an organic compound layer, a sulfate suchas lithium sulfate (LiSO₄), potassium sulfate (K₂SO₄), sodium sulfate(Na₂SO₄), magnesium sulfate (MgSO₄), calcium sulfate (CaSO₄), strontiumsulfate (SrSO₄), barium sulfate (BaSO₄), titanium sulfate (Ti(SO₄)₃),zirconium sulfate (Zr(SO₄)₂), manganese sulfate (MnSO₄), iron sulfate(FeSO₄), ferric sulfate (Fe₂(SO₄)₃), cobalt sulfate (COSO₄), cobaltsulfate (CO₂(SO₄)₃), nickel sulfate (NiSO₄), copper sulfate (CuSO₄),silver sulfate (Ag₂SO₄), zinc sulfate (ZnSO₄), aluminum sulfate(Al₂(SO₄)₃), indium sulfate (In₂(SO₄)₃), tin sulfate (SnSO₄), tinsulfate (Sn(SO₄)₂), antimony sulfate (Sb₂(SO₄)₃), or bismuth (III)sulfate (Bi₂(SO₄)₃) can be used.

In the present invention, as another inorganic insulator that can beused for an insulator mixed into an organic compound layer, a nitratesuch as lithium nitrate (LiNO₃), potassium nitrate (KNO₃), sodiumnitrate (NaNO₃), magnesium nitrate (Mg(NO₃)₂), calcium nitrate(Ca(NO₃)₂), strontium nitrate (Sr(NO₃)₂), barium nitrate (Ba(NO₃)₂),titanium nitrate (Ti(NO₃)₄), strontium nitrate (Sr(NO₃)₂), bariumnitrate (Ba(NO₃)₂), zirconium nitrate (Zr(NO₃)₄), manganese nitrate(Mn(NO₃)₂), iron nitrate (Fe(NO₃)₂), iron nitrate (Fe(NO₃)₃), cobaltnitrate (Co(NO₃)₂), nickel nitrate (Ni(NO₃)₂), copper nitrate(Cu(NO₃)₂), silver nitrate (AgNO₃), zinc nitrate (Zn(NO₃)₂), aluminumnitrate (Al(NO₃)₃), indium nitrate (In(NO₃)₃), tin nitrate (Sn(NO₃)₂),or bismuth (III) nitrate (Bi(NO₃)₃) can be used.

In the present invention, as another inorganic insulator that can beused for an insulator mixed into an organic compound layer, a nitridesuch as aluminum nitrite (AlN) and silicon nitrite (SiN); and acarboxylate such as lithium carboxylate (CH₃COOLi), potassium acetate(CH₃COOK), sodium acetate (CH₃COONa), magnesium acetate (Mg(CH₃COO)₂),calcium acetate (Ca(CH₃COO)₂), strontium acetate (Sr(CH₃COO)₂), orbarium acetate (Ba(CH₃COO)₂) can be used.

In the present invention, as an inorganic insulator that can be used foran insulator mixed into an organic compound layer, one or plural kindsof the above inorganic insulators can be used.

In the present invention, as an organic compound that can be used for aninsulator mixed into an organic compound layer, a compound in whichcarriers are difficult to be injected and a band gap is 3.5 eV or more,preferably, 4 eV or more and 6 eV or less, can be used. For example,polyimide, acrylic, polyamide, benzocyclobutene, polyester, a novolacresin, a melamine resin, a phenol resin, an epoxy resin, a siliconresin, a furan resin, a diallyl phthalate resin, or a siloxane resin canbe used. It is to be noted that the siloxane resin corresponds to resinincluding a Si—O—Si bond. Siloxane includes a skeleton structure formedfrom a bond of silicon (Si) and oxygen (O).

In the present invention, as an organic compound that can be used for aninsulator mixed into an organic compound layer, one or plural kinds ofthe above organic compounds can be used.

In the present invention, as an insulator mixed into an organic compoundlayer, one or plural kinds of the above inorganic insulators and organiccompounds can be used.

Further, an element, a compound, or the like having high conductivity isused for the first conductive layer 50, the first conductive layer 60,the first conductive layer 70, the first conductive layer 80, the secondconductive layer 53, the second conductive layer 63, the secondconductive layer 73, and the second conductive layer 83. Typically, asingle layer or a stacked layer formed using one element selected fromgold (Au), platinum (Pt), nickel (Ni), tungsten (W), molybdenum (Mo),iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), carbon (C),aluminum (Al), manganese (Mn), and titanium (Ti) or an alloy containinga plurality of the elements can be used. As the alloy containing aplurality of the elements, for example, an alloy containing Al and Ti,an alloy containing Al, Ti, and C, an alloy containing Al and Ni, analloy containing Al and C, an alloy containing Al, Ni, and C, an alloycontaining Al and Mo, or the like can be used.

The first conductive layer 50, the first conductive layer 60, the firstconductive layer 70, the first conductive layer 80, the secondconductive layer 53, the second conductive layer 63, the secondconductive layer 73, and the second conductive layer 83 can be formed byusing an evaporation method, sputtering, a CVD method, a printingmethod, a dispenser method, or a droplet discharging method.

One or both of the first conductive layer 50, the first conductive layer60, the first conductive layer 70, and the first conductive layer 80;and the second conductive layer 53, the second conductive layer 63, thesecond conductive layer 73, and the second conductive layer 83 may beprovided so as to transmit light. A light-transmitting conductive layeris formed of a transparent conductive material. Alternatively, thelight-transmitting conductive layer may be formed with a thickness sothat light can pass therethrough when the transparent conductive layeris not used. As the transparent conductive material, indium tin oxide(ITO), zinc oxide (ZnO), indium zinc oxide (IZO), zinc oxide added withgallium (GZO), or other light-transmitting oxide conductive materialssuch as an indium oxide containing tungsten oxide, an indium zinc oxidecontaining tungsten oxide, an indium oxide containing titanium oxide, oran indium tin oxide containing titanium oxide can be used. Indium tinoxide and silicon oxide (hereinafter, referred to as ITSO), or an oxideconductive material formed using a target in which 2 wt % to 20 wt % ofzinc oxide (ZnO) is mixed into indium oxide containing silicon oxide maybe used.

The organic compound layer 52, the organic compound layer 62, theorganic compound layer 72, and the organic compound layer 82 are formedusing an organic compound, an organic compound of which the conductivityis changed by electric action, or a layer in which an organic compoundand an inorganic compound are mixed.

As an inorganic insulator that can form the organic compound layer 52,the organic compound layer 62, the organic compound layer 72, and theorganic compound layer 82, silicon oxide, silicon nitride, siliconoxynitride, silicon nitride oxide, or the like can be used.

As an organic compound that can form the organic compound layer 52, theorganic compound layer 62, the organic compound layer 72, and theorganic compound layer 82, an organic resin typified by polyimide,acrylic, polyamide, benzocyclobutene, an epoxy resin, or the like can beused.

Further, as an organic compound of which the conductivity is changed byelectric action, which can form the organic compound layer 52, theorganic compound layer 62, the organic compound layer 72, and theorganic compound layer 82, an organic compound material that has a holetransporting property or an organic compound material that has anelectron transporting property can be used.

As an organic compound material having a hole transporting property, anaromatic amine compound (in other words, a compound having a benzenering-nitrogen bond) such as4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl (abbreviation: α-NPD),4,4′-bis[N-(3-methylphenyl)-N-phenyl-amino]-biphenyl (abbreviation:TPD), 4,4′,4″-tris(N,N-diphenyl-amino)-triphenylamine (abbreviation:TDATA), 4,4′,4″-tris[N-(3-methylphenyl)-N-phenyl-amino]-triphenylamine(abbreviation: MTDATA), or4,4′-bis(N-(4-(N,N-di-m-tolylamino)phenyl)-N-phenylamino)biphenyl(abbreviation: DNTPD); or a phthalocyanine compound such asphthalocyanine (abbreviation: H₂Pc), copper phthalocyanine(abbreviation: CuPc), or vanadyl phthalocyanine (abbreviation: VOPc) canbe used. The substances described here are mainly substances having holemobility of 10⁻⁶ cm²/Vs or more, further preferably, 10⁻⁶ cm²/Vs or moreand 10⁻² cm²/Vs or less.

As an organic compound material having a electron transporting property,a material formed of a metal complex having a quinoline skeleton or abenzoquinoline skeleton such as tris(8-quinolinolato)aluminum(abbreviation: Alq₃), tris(4-methyl-8-quinolinolato)aluminum(abbreviation: Almq₃), bis(10-hydroxybenzo[h]-quinolinato)beryllium(abbreviation: BeBq₂), orbis(2-methyl-8-quinolinolato)-4-phenylphenolato-aluminum (abbreviation:BAlq), or the like can be used. Alternatively, a material of a metalcomplex having an oxazole or thiazole ligand such asbis[2-(2-hydroxyphenyl)benzoxazolate]zinc (abbreviation: Zn(BOX)₂) orbis[2-(2-hydroxyphenyl)benzothiazolate]zinc (abbreviation: Zn(BTZ)₂), orthe like can be used. In addition to the metal complex,2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD); 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene(abbreviation: OXD-7);3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: TAZ);3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ); bathophenanthroline (abbreviation: BPhen);bathocuproin (abbreviation: BCP); or the like can be used. Thesubstances described here are mainly substances having electron mobilityof 10⁻⁶ cm²/Vs or more, further preferably, 10⁻⁶ cm²/Vs or more and 10⁻²cm²/Vs or less.

In the present invention, as an organic compound material that can beused for an organic compound layer, one or plural kinds of the aboveorganic compound materials can be used.

It is to be noted that the organic compound layer 52, the organiccompound layer 62, the organic compound layer 72, and the organiccompound layer 82 are formed to have such a film thickness thatconductivity of the memory element is changed by electric action.

In addition, a rectifying element may be provided between the firstconductive layer 50 and the organic compound layer 52; the firstconductive layer 60 and the organic compound layer 62; the firstconductive layer 70 and the organic compound layer 72; and the firstconductive layer 80 and the organic compound layer 82, respectively. Therectifying element typically refers to a transistor or a diode in whicha gate electrode and a drain electrode are connected. For example, a PNjunction diode provided by stacking an n-type semiconductor layer and ap-type semiconductor layer can be used. In this manner, since a currentflows only in one direction by providing the diode having rectification,errors are reduced and margin of reading is improved. In the case ofproviding a diode, not only a diode having a PN junction but also adiode having another structure such as a diode having a PIN junction oran avalanche diode may be provided. It is to be noted that therectifying element may be provided between the organic compound layer52, the organic compound layer 62, the organic compound layer 72, andthe organic compound layer 82; and the second conductive layer 53, thesecond conductive layer 63, the second conductive layer 73, and thesecond conductive layer 83.

In accordance with the memory element of the present invention,characteristics of a writing voltage of the memory element and the likeare stabilized without variation; therefore, normal writing in eachelement can be performed. Further, since a carrier injecting property isimproved by a tunnel current of the insulator, a film thickness of anorganic compound layer can be increased. In addition, since a defectinside of a layer such as crystallization can be prevented due to amixed layer of an insulator and an organic compound, a state of theorganic compound layer is stabilized. Therefore, a defect in which thememory element is short-circuited in an initial state before havingconductivity can be prevented. As a result, a memory device and asemiconductor device, each of which has high reliability, can beprovided with high yield.

Embodiment Mode 2

In the present embodiment mode, an example of a structure of a memoryelement included in a memory device of the present invention will bedescribed with reference to drawings.

The memory element shown in Embodiment Mode 1 shows an example in whicha plurality of insulators are mixed into the organic compound layerprovided between a pair of conductive layers. In the present embodiment,the insulators are mixed into at least one of the pair of the conductivelayers provided as electrodes as well as into the organic compoundlayer.

A memory element shown in FIG. 17A is an example of a memory element ofthe present invention, in which an organic compound layer 57 including afirst insulator 56 is formed over a first conductive layer 55 includinga second insulator 59, and a second conductive layer 58 is formed overthe organic compound layer 57.

A memory element shown in FIG. 17B is an example of a memory element ofthe present invention, in which an organic compound layer 67 including afirst insulator 66 is formed over a first conductive layer 65, and asecond conductive layer 68 including a second insulator 69 is formedover the organic compound layer 67.

A memory element shown in FIG. 17C is an example of a memory element ofthe present invention, in which an organic compound layer 77 including afirst insulator 76 is formed over a first conductive layer 75 includinga second insulator 88, and a second conductive layer 78 including athird insulator 79 is formed over the organic compound layer 77.

FIGS. 17A to 17C are schematic views showing an example in which aplurality of particulate insulators are mixed in the organic compoundlayer and the conductive layers so as to describe a plurality ofinsulators mixed in the organic compound layer and the conductive layersclearly. Therefore, a size of the insulators and a mixed state are notnecessary to be the same as the states shown in FIGS. 17A to 17C. Aconcentration of the insulator and the like can be controlledarbitrarily as shown in FIGS. 16A to 16C depending on a material usedfor an organic compound and a conductive layer, and a forming method.The mentioned above can be employed in other drawings in the presentspecification.

Each of the first conductive layer 55, the first conductive layer 65,the first conductive layer 75, the second conductive layer 58, thesecond conductive layer 68, and the second conductive layer 78 can beformed by using any one of the materials and the forming methods of thefirst conductive layer 50 and the second conductive layer 53 describedin Embodiment Mode 1.

Further, the first insulator 56, the first insulator 66, the firstinsulator 76, the second insulator 59, the second insulator 69, thesecond insulator 79, the third insulator 88, the organic compound layer57, the organic compound layer 67, and the organic compound layer 77 canbe provided by using a similar material and forming method of theinsulators and the organic compound layers shown in Embodiment Mode 1.In the first insulators, the second insulators, and the thirdinsulators, the same material may be used, and different materials maybe used for each insulator.

When an insulator exists at an interface of an organic compound layerand a conductive layer, a tunnel injection of carriers between theorganic compound layer and the conductive layer becomes possible.Therefore, characteristics of a writing voltage of a memory element andthe like are stabilized without variation, and normal writing in eachelement can be performed. As shown in FIGS. 17A to 17C, when a pluralityof insulators are mixed into the first conductive layers and the secondconductive layers as well as into the organic compound layers,possibility of existing insulators at the interface of each of theorganic compound layers and each of the first conductive layers or theinterface of each of the organic compound layers and each of the secondconductive layers is increased. Accordingly, a sufficient tunnelinjection effect of the insulator is easily obtained. Further, since aplurality of insulators are mixed in the organic compound layer, adefect inside a layer due to crystallization of the organic compound andthe like can be prevented; therefore, condition of the organic compoundlayer is stabilized. In addition, since a carrier injecting property isimproved by the tunnel injection, a thickness of the organic compoundlayer can be thickened. Therefore, a defect in which a memory element isshort-circuited in an initial state before having conductivity can beprevented.

Further, the first insulator 56, the first insulator 66, and the firstinsulator 76 existing respectively in the organic compound layer 57, theorganic compound layer 67, and the organic compound layer 77 do nottransport carriers. Therefore, a carrier transporting property of theentire organic compound layer 57, organic compound layer 67, and organiccompound layer 77 is reduced due to obstruction of the first insulator56, the first insulator 66, and the first insulator 76. Thus, even in anorganic compound material having a high carrier transporting property, acurrent value that is necessary for short-circuit (writing into anelement) is reduced to bring an advantage such as a low powerconsumption and expansion of selection range of a material.

From the above, a memory element and a semiconductor device having highreliability can be provided with high yield.

Embodiment Mode 3

In the present embodiment mode, an example of a structure of a memoryelement included in a memory device of the present invention will bedescribed with drawings. More specifically, a case where a structure ofa memory device is a passive matrix type will be shown.

FIG. 3 shows a configuration example of a memory device of the presentinvention. The memory device includes a memory cell array 722 providedwith memory cells 721 in a matrix; a bit line driving circuit 726 havinga column decoder 726 a, a reading circuit 726 b, and a selector 726 c; aword line driving circuit 724 having a row decoder 724 a and a levelshifter 724 b; and an interface 723 having a writing circuit and thelike and communicating with outside. It is to be noted that aconfiguration of a memory device 716 shown here is only one example. Thememory device 716 may include a sense amplifier, an output circuit, abuffer, and the like, and the writing circuit may be provided in the bitline driving circuit.

The memory cell 721 includes a first conductive layer forming a wordline Wy (1≦y≦n), a second conductive layer forming a bit line Bx(1≦x≦m), and an insulting layer. The insulating layer is provided by asingle layer or a stacked layer between the first conductive layer andthe second conductive layer.

FIG. 2A shows a top view of the memory cell array 722, FIGS. 2B and 2Cshow cross-sectional views taken along line A-B in FIG. 2A. In FIG. 2A,an insulating layer 754 is omitted; however, the insulating layer 754 isprovided as shown in FIG. 2B.

The memory cell array 722 includes a first conductive layer 751 a, afirst conductive layer 751 b, and a first conductive layer 751 c, whichextend in a first direction; an organic compound layer 752 including aplurality of insulators 756 that is provide to cover the firstconductive layer 751 a, the first conductive layer 751 b, and the firstconductive layer 751 c; and a second conductive layer 753 a, a secondconductive layer 753 b, and a second conductive layer 753 c, whichextend in a second direction being perpendicular to the first direction(see FIG. 2A). The organic compound layer 752 including a plurality ofinsulators 756 is provided between the first conductive layer 751 a, thefirst conductive layer 751 b, and the first conductive layer 751 c; andthe second conductive layer 753 a, the second conductive layer 753 b,and the second conductive layer 753 c. Further, the insulating layer 754serving as a protective film is provided to cover the second conductivelayer 753 a, the second conductive layer 753 b, and the secondconductive layer 753 c (see FIG. 2B). When influence of an electricfield in lateral directions between each adjacent memory cell isconcerned, the organic compound layer 752 including a plurality ofinsulators 756 that is provided in each memory cell may be isolated.

FIG. 2C is a modified example of FIG. 2B. Over a substrate 790, a firstconductive layer 791 a, a first conductive layer 791 b, a firstconductive layer 791 c, an organic compound layer 792 including aplurality of insulators 796, a second conductive layer 793 b, and aninsulating layer 794 that is a protective film are formed. A shape ofthe first conductive layers may have a taper shape or a shape in which aradius of curvature is varied continuously similar to the firstconductive layers 791 a, 791 b, and 791 c in FIG. 2C. A shape such asthe first conductive layers 791 a, 791 b, and 791 c can be formed withthe use of a droplet discharging method or the like. A curved surfacehaving such a curvature provides favorable coverage of stackedinsulating layers or conductive layers.

Mixed condition of the insulators in the organic compound layer of thepresent embodiment mode is only an example. A concentration of theinsulators or the like can be arbitrarily controlled depending on aproperty or a size of a material used for an insulator, a material usedfor an organic compound and a conductive layer, and a forming method asshown in FIGS. 16A to 16C. For example, a concentration of insulatorsmay be gradually increased toward an interface of an organic compoundlayer and a first conductive layer and an interface of an organiccompound layer and a second conductive layer. Further, its concentrationmay be changed continuously or discontinuously in the organic compoundlayer.

Further, a partition wall (insulating layer) may be formed to cover anedge of a first conductive layer. The partition wall (insulating layer)serves as a wall dividing between a memory element and other memoryelements. FIGS. 8A and 8B show a structure in which the partition wall(insulating layer) covers the edge of the first conductive layer.

In an example of a memory element shown in FIG. 8A, a partition wall(insulating layer) 775 is formed into a shape having a taper to coveredges of a first conductive layer 771 a, a first conductive layer 771 b,and a first conductive layer 771 c. The partition wall (insulatinglayer) 775 is formed over the first conductive layers 771 a, 771 b, and771 c provided over a substrate 770, and then, an organic compound layer772 including a plurality of insulators 776, a second conductive layer773 b, and an insulating layer 774 are formed.

An example of a memory element shown in FIG. 8B is a shape in which apartition wall (insulating layer) 765 has a curvature, and a radius ofthe curvature is varied continuously. Over a substrate 760, a firstconductive layer 761 a, a first conductive layer 761 b, a firstconductive layer 761 c, an organic compound layer 762 including aplurality of insulators 766, a second conductive layer 763 b, and aninsulating layer 764 are formed.

In the structures of the above memory cells, a quartz substrate, asilicon substrate, a metal substrate, a stainless-steel substrate, orthe like, in addition to a glass substrate and a flexible substrate canbe used for the substrate 750, the substrate 760, the substrate 770, andthe substrate 790. The flexible substrate is a substrate that can bebent flexibly, such as a plastic substrate formed of polycarbonate,polyarylate, polyether sulfone, or the like. In addition, an attachmentfilm (having polypropylene, polyester, vinyl, polyvinyl fluoride,polyvinyl chloride or the like), paper of a fibrous material, a basematerial film (polyester, polyamide, an inorganic vapor deposition film,paper, or the like), or the like can be used. Alternatively, the memorycell array 722 can be provided over a field effect transistor (FET)formed over a semiconductor substrate such as a Si substrate, or over athin film transistor (TFT) formed over a substrate such as a glasssubstrate.

A material and a forming method of the first conductive layers 751 a to751 c, the first conductive layers 761 a to 761 c, the first conductivelayers 771 a to 771 c, the first conductive layers 791 a to 791 c, thesecond conductive layers 753 a to 753 c, the second conductive layers763 a to 763 c, the second conductive layers 773 a to 773 c, and thesecond conductive layers 793 a to 793 c shown in the present embodimentmode can employ any one of the materials and the forming methods of thefirst conductive layer 50 and the second conductive layer 53 shown inEmbodiment Mode 1 in the similar way.

Further, the insulator 756, the insulator 776, the insulator 796, theorganic compound layer 752, the organic compound layer 762, the organiccompound layer 772, and the organic compound layer 792 can be providedby using the similar material and forming method of the insulators andthe organic compound layers shown in Embodiment Mode 1.

In addition, a rectifying element may be provided between the firstconductive layers 751 a to 751 c and the organic compound layer 752; thefirst conductive layers 761 a to 761 c and the organic compound layer762; the first conductive layers 771 a to 771 c and the organic compoundlayer 772; and the first conductive layers 791 a to 791 c and theorganic compound layer 792, respectively. It is to be noted that therectifying element may be provided between the organic compound layer752 and the second conductive layers 753 a to 753 c; the organiccompound layer 762 and the second conductive layers 763 a to 763 c; theorganic compound layer 772 and the second conductive layers 773 a to 773c; and the organic compound layer 792 and the second conductive layers793 a to 793 c, respectively.

As the partition wall (insulating layer) 765 and the partition wall(insulating wall) 775, silicon oxide, silicon nitride, siliconoxynitride, aluminum oxide, aluminum nitride, aluminum oxynitride, oranother inorganic insulating material; acrylic acid, methacrylic acid,or a derivative thereof; a heat-resistant high molecular compound suchas polyimide, aromatic polyamide, or polybenzimidazole; or a siloxanematerial may be used. Alternatively, a resin material such as a vinylresin of polyvinyl alcohol, polyvinylbutyral; or the like, an epoxyresin, a phenol resin, a novolac resin, an acrylic resin, a melamineresin, a urethane resin, or the like is used. Further, an organicmaterial such as benzocyclobutene, parylene, arylenether fluoride, orpolyimide; a composition material containing a water-soluble homopolymerand a water-soluble copolymer; or the like may be used. As amanufacturing method, a vapor phase growth method such as a plasma CVDmethod or a thermal CVD method, or sputtering can be used. A dropletdischarging method, a dispenser method, or a printing method (a methodfor forming a pattern, such as screen printing or offset printing) canalso be used. A TOF film and an SOG film obtained by a coating methodcan also be used.

After forming a conductive layer, an insulating layer or the like bydischarging a composition by a droplet discharging method, a surfacethereof may be planarized by pressing with pressure to improveplanarity. As a pressing method, unevenness of the surface may bereduced by moving a roller-shaped object over the surface, or thesurface may be perpendicularly pressed with a flat plate-shaped object.A heating step may also be performed at the time of pressing.Alternatively, the unevenness of the surface may be eliminated with anair knife after softening or melting the surface with a solvent or thelike. A CMP method may be also used for polishing the surface. This stepcan be employed in planarizing a surface when unevenness is generated bya droplet discharging method.

In accordance with the memory element of the present invention,characteristics of a writing voltage of the memory element and the likeare stabilized without variation; therefore, normal writing in eachelement can be performed. Further, since a carrier injecting property isimproved by a tunnel current of the insulator, a film thickness of anorganic compound layer can be thickened. In addition, since a defectinside of a layer such as crystallization of an organic compound can beprevented due to a mixed layer of an insulator and an organic compound,condition of the organic compound layer is stabilized. Therefore, adefect in which the memory element is short-circuited in an initialstate before having conductivity can be prevented. As a result, a memorydevice and a semiconductor device, each of which has high reliability,can be provided with high yield.

Embodiment Mode 4

In the present embodiment mode, a memory device having a differentstructure from that of Embodiment Mode 3 will be described.Specifically, the case where the structure of the memory device is anactive matrix type will be shown.

FIG. 5 shows a configuration example of a memory device that is shown inthe present embodiment mode. The memory device includes a memory cellarray 232 provided with memory cells 231 in a matrix; a bit line drivingcircuit 226 having a column decoder 226 a, a reading circuit 226 b, anda selector 226 c; a word line driving circuit 224 having a row decoder224 a and a level shifter 224 b; and a interface 223 having a writingcircuit and the like and communicating with outside. It is to be notedthat a configuration of a memory device 217 shown here is only oneexample. The memory device 217 may include other circuits such as asense amplifier, an output circuit, and a buffer, and the like. Thewriting circuit may be provided in the bit line driving circuit.

The memory cell array 232 includes a first wiring forming a word line Wy(1≦y≦n), a second wiring forming a bit line Bx (1≦x≦m), a transistor 210a, a memory element 215 b, and the memory cell 231. The memory element215 b has a structure in which an organic compound layer is interposedbetween a pair of conductive layers.

FIG. 4A shows a top view of the memory cell array 232, and FIG. 4B showsa cross-sectional view taken along a line E-F in FIG. 4A. Although anorganic compound layer 212 including a plurality of insulators 216, asecond conductive layer 213, and an insulating layer 214 are omitted inFIG. 4A, each of them is provided as shown in FIG. 4B.

In the memory cell array 232, a first wiring 205 a and a first wiring205 b each of which are extended in a first direction, and a secondwiring 202 of which is extended in a second direction that isperpendicular to the first direction, are provided in a matrix. Each ofthe first wirings is connected to a source electrode or a drainelectrode of each transistor 210 a and transistor 210 b. The secondwiring is connected to each gate electrode of the transistor 210 a andthe transistor 210 b. Further, each of a first conductive layer 206 aand a first conductive layer 206 b is connected to a source electrode ora drain electrode of the transistors 210 a and 210 b, which are notconnected with the first wirings. Then, an organic compound layer 212including a plurality of insulators 216 and the second conductive layer213 are stacked over each of the first conductive layer 206 a and thefirst conductive layer 206 b to provide a memory element 215 a and amemory element 215 b. Partition walls (insulating layers) 207 areprovided between adjacent each memory cell 231, and the organic compoundlayer 212 including a plurality of insulators 216 and the secondconductive layer 213 are stacked over the first conductive layers andthe partition walls (insulating layers) 207. An insulating layer 214 isprovided over the second conductive layer 213 as a protective layer.Further, as the transistors 210 a and 210 b, thin film transistors areemployed (see FIG. 4B).

A memory device in FIG. 4B is provided over a substrate 200, whichincludes an insulating layer 201 a; an insulating layer 201 b; aninsulating layer 208; an insulating layer 209; an insulating layer 211;a semiconductor layer 204 a, a gate electrode layer 202 a, and thewiring 205 a serving as a source electrode or a drain electrode formingthe transistor 210 a; and a semiconductor layer 204 b, a gate electrodelayer 202 b and a wiring 205 b serving as a source electrode or a drainelectrode forming the transistor 210 b. The organic compound layer 212including a plurality of insulators 216 and the second conductive layer213 are formed over the first conductive layer 206 a, the firstconductive layer 206 b, and the partition walls (insulating layers) 207.Mixed condition of the insulators in the organic compound layer of thepresent embodiment mode is only an example. A concentration of theinsulators or the like can be arbitrarily controlled depending on aproperty or a size of a material used for an insulator, a material usedfor an organic compound and a conductive layer, and a forming method asshown in FIGS. 16A to 16C. For example, a concentration of insulatorsmay be gradually increased toward an interface of an organic compoundlayer and a first conductive layer and an interface of an organiccompound layer and a second conductive layer. Further, the concentrationmay be changed continuously or discontinuously in the organic compoundlayer.

In the present embodiment mode, the organic compound layer 212 includinga plurality of insulators 216, which forms a memory element included ina memory device, is formed over the first conductive layer. When avoltage is applied between the first conductive layer and the secondconductive layer, a current flows in the organic compound layer 212,which generates heat (Joule heat). Then, when a temperature of theorganic compound layer rises to a glass-transition temperature by Jouleheat, a material forming the organic compound layer 212 becomes acomposition having fluidity. The composition having fluidity flowswithout keeping a shape of a solid state. Therefore, a film thickness ofthe organic compound layer is uneven, and the organic compound layer istransformed. Then, the first conductive layer and the second conductivelayer are connected with each other. As a result, the first conductivelayer and the second conductive layer are short-circuited. Therefore,conductivity of the memory element is changed before and after applyinga voltage.

A tunnel injection of carriers from the first conductive layer to theorganic compound layer 212 becomes possible due to the insulator 216existing at an interface of the organic compound layer 212 and the firstconductive layer. Therefore, characteristics of a writing voltage of thememory element and the like are stabilized without variation; therefore,normal writing in each element can be performed. Further, since a defectsuch as crystallization of an organic compound can be prevented due to amixed layer of a plurality of insulators and an organic compound,condition of the organic compound layer is stabilized. In addition,since a carrier injecting property is improved by the tunnel injection,a film thickness of the organic compound layer can be thickened.Therefore, a defect in which the memory element is short-circuited in aninitial state before having conductivity can be prevented.

Further, the insulator 216 existing in the organic compound layer 212does not transport carriers. Therefore, a carrier transporting propertyof the entire organic compound layer 212 is reduced due to obstructionof the insulator 216. Thus, even in an organic compound material havinga high carrier transporting property, a current value that is necessaryfor short-circuit (writing into an element) is reduced to bring anadvantage such as low power consumption and expansion of selection rangeof a material.

As shown in FIG. 6, a memory element 265 a and a memory element 265 bmay be connected to a field effect transistor 260 a and a field effecttransistor 260 b provided over a single crystal semiconductor substrate250. Here, an insulating layer 270 is provided to cover source or drainelectrode layers 255 a to 255 d of the field effect transistor 260 a andthe field effect transistor 260 b. Over the insulating layer 270, afirst conductive layer 256 a, a first conductive layer 256 b, apartition wall (insulating layer) 267, an organic compound layer 262 aincluding a plurality of insulators 266 a, an organic compound layer 262b including a plurality of insulators 266 b, and a second conductivelayer 263 are provided to form a memory element 265 a and a memoryelement 265 b. An organic compound layer including an insulator may beselectively provided by using a mask or the like in each memory cell inthe same manner as the organic compound layers 262 a including aplurality of insulators 266 a and the organic compound layer 262 bincluding a plurality of insulators 266 b. Further, the memory deviceshown in FIG. 6 also includes an element isolation region 268, aninsulating layer 269, an insulating layer 261, and an insulating layer264. The organic compound layer 262 a including a plurality ofinsulators 266 a and the organic compound layer 262 b including aplurality of insulators 266 b are formed over the first conductive layer256 a, the first conductive layer 256 b, and the partition wall 267. Asecond conductive layer 263 is formed thereover. Mixed condition of theinsulators in the organic compound layer of the present embodiment modeis only an example. A concentration of the insulators or the like can bearbitrarily controlled depending on a property or a size of a materialused for an insulator, a material used for an organic compound and aconductive layer, and a forming method as shown in FIGS. 16A to 16C. Forexample, a concentration of insulators may be gradually increased towardan interface of an organic compound layer and a first conductive layerand an interface of an organic compound layer and a second conductivelayer. Further, the concentration may be changed continuously ordiscontinuously in the organic compound layer.

In the present embodiment mode, the organic compound layer 262 aincluding a plurality of insulators 266 a and the organic compound layer262 b including a plurality of insulators 266 b, which form memoryelements included in a memory device, are formed over the firstconductive layer. When a voltage is applied between the first conductivelayer and the second conductive layer, a current flows in the organiccompound layer 262 a and the organic compound layer 262 b, whichgenerates heat (Joule heat). Then, when a temperature of the organiccompound layer rises to a glass-transition temperature by Joule heat, amaterial forming the organic compound layer 262 a and the organiccompound layer 262 b become a composition having fluidity. Thecomposition having fluidity flows without keeping a shape of a solidstate. Therefore, a film thickness of the organic compound layer isuneven, and the organic compound layer is transformed. Then, the firstconductive layer and the second conductive layer are connected with eachother. As a result, the first conductive layer and the second conductivelayer are short-circuited. Therefore, conductivity of the memory elementis changed before and after applying a voltage.

A tunnel injection of carriers from the first conductive layer to eachof the organic compound layer 262 a and the organic compound layer 262 bbecomes possible due to the insulator 266 a and the insulator 266 bexisting at an interface of the organic compound layer 262 a and thefirst conductive layer and at an interface of the organic compound layer262 b and the first conductive layer. Therefore, characteristics of awriting voltage of the memory element and the like are stabilizedwithout variation; therefore, normal writing in each element can beperformed. Further, since a defect such as crystallization of an organiccompound can be prevented due to a mixed layer of a plurality ofinsulators and an organic compound, condition of the organic compoundlayer is stabilized. In addition, since a carrier injecting property isimproved by a tunnel injection, a film thickness of the organic compoundlayer can be thickened. Therefore, a defect in which the memory elementis short-circuited in an initial state before having conductivity can beprevented.

Further, the insulator 266 a and the insulator 266 b existingrespectively in the organic compound layer 262 a and the organiccompound layer 262 b do not transport carriers. Therefore, a carriertransporting property of the entire organic compound layers 262 a and262 b is reduced due to obstruction of the insulator 266 a and theinsulator 266 b. Thus, even in an organic compound material having ahigh carrier transporting property, a current value that is necessaryfor short-circuit (writing into an element) is reduced to bring anadvantage such as low power consumption and expansion of selection rangeof a material.

As described above, the first conductive layer can be arranged freely byproviding the insulating layer 270 to form a memory element.Accordingly, in the structure of FIG. 4B, the memory elements 215 a and215 b are required to be provided in the regions where the source ordrain electrode layers of the transistors 210 a and 210 b are notprovided; however, for example, it is possible to form the memoryelements 215 a and 215 b in the upper side of the transistors 210 a and210 b by employing the above structure. As a result, the memory device217 can be more highly integrated.

Furthermore, the transistor 210 a and the transistor 210 b can beprovided in any structure as far as the transistors 210 a and 210 b canserve as a switching element. As a semiconductor layer, various types ofsemiconductors such as an amorphous semiconductor, a crystallinesemiconductor, a multicrystalline semiconductor, and a microcrystallinesemiconductor can be used, and an organic transistor may be formed byusing an organic compound. FIG. 4A shows an example of providing aplanar thin film transistor over an insulating substrate; however, atransistor can also be formed to have a staggered structure, an invertedstaggered structure, or the like.

FIG. 7 shows an example of using a thin film transistor having aninverted staggered structure. A transistor 290 a and a transistor 290 b,which are thin film transistors having an inverted staggered structure,are provided over a substrate 280. The transistor 290 a includes aninsulating layer 288, a gate electrode layer 281, an amorphoussemiconductor layer 282, a semiconductor layer 283 a having oneconductivity type, a semiconductor layer 283 b having one conductivitytype, and a source or drain electrode layer 285. The source or drainelectrode layer is a first conductive layer 286 a and a first conductivelayer 286 b forming a memory element. A partition wall (insulatinglayer) 287 is stacked to cover edges of the first conductive layers 286a and 286 b. An organic compound layer 292 including a plurality ofinsulators 296 a and a plurality of insulators 296 b, a secondconductive layer 293, and an insulating layer 294 that is a protectivelayer are formed over the first conductive layers 286 a and 286 b andthe partition wall (insulating layer) 287 to form a memory element 295 aand a memory element 295 b. The insulator 296 a and the insulator 296 bin the organic compound layer 292 are selectively added into regions ofthe memory element 295 a and the memory element 295 b, which areinterposed between the first conductive layer 286 a and the secondconductive layer 293; and the first conductive layer 286 b and thesecond conductive layer 293, respectively. In such a manner, theinsulator may be selectively mixed into the organic compound layer. Inthe memory device shown in FIG. 7 of the present embodiment mode, theinsulator 296 a and the insulator 296 b are selectively added into theorganic compound layer 292 by using a doping method, an ion injectingmethod, or the like. Mixed condition of the insulators in the organiccompound layer of the present embodiment mode is only an example. Aconcentration of the insulators or the like can be arbitrarilycontrolled depending on a property or a size of a material used for aninsulator, a material used for an organic compound and a conductivelayer, and a forming method as shown in FIGS. 16A to 16C. For example, aconcentration of insulators may be gradually increased toward aninterface of an organic compound layer and a first conductive layer andan interface of an organic compound layer and a second conductive layer.Further, the concentration may be changed continuously ordiscontinuously in the organic compound layer.

In the memory device shown in FIG. 7 of the present embodiment mode, theorganic compound layer 292 including the insulator 296 a and 296 b,which forms a memory element included in the memory device, is formedover the first conductive layer. When a voltage is applied between thefirst conductive layer and the second conductive layer, a current flowsin the organic compound layer 292, which generates heat (Joule heat).Then, when a temperature of the organic compound layer rises to aglass-transition temperature by Joule heat, a material forming theorganic compound layer 292 becomes a composition having fluidity. Thecomposition having fluidity flows without keeping a shape of a solidstate. Therefore, a film thickness of the organic compound layer isuneven, and the organic compound layer is transformed. Then, the firstconductive layer and the second conductive layer are connected with eachother. As a result, the first conductive layer and the second conductivelayer are short-circuited. Therefore, conductivity of the memory elementis changed before and after applying a voltage.

A tunnel injection of carriers from the first conductive layer to theorganic compound layer 292 becomes possible due to the insulator 296 aand the insulator 296 b each existing at an interface of the organiccompound layer 292 and the first conductive layer. Therefore,characteristics of a writing voltage of the memory element and the likeare stabilized without variation; therefore, normal writing in eachelement can be performed. Further, since a plurality of insulators aremixed in an organic compound layer, a defect such as crystallization ofan organic compound can be prevented, condition of an organic compoundlayer is stabilized. In addition, since a carrier injecting property isimproved by a tunnel injection, a film thickness of the organic compoundlayer can be thickened. Therefore, a defect in which the memory elementis short-circuited in an initial state before having conductivity can beprevented.

Further, the insulator 296 a and the insulator 296 b each existing inthe organic compound layer 292 do not transport carriers. Therefore, acarrier transporting property of the entire organic compound layer 292is reduced due to obstruction of the insulator 296 a and the insulator296 b. Thus, even in an organic compound material having a high carriertransporting property, a current value that is necessary forshort-circuit (writing into an element) is reduced to bring an advantagesuch as low power consumption and expansion of selection range of amaterial.

In the memory device shown in FIG. 7, a gate electrode 281, the sourceor drain electrode layer 285, the first conductive layers 286 a and 286b, and the partition wall (insulating layer) 287 are formed by using adroplet discharging method. A droplet discharging method is a method inwhich a composition containing a component forming material, which isfluid, is discharged (Jetted) as a droplet to form a desired pattern. Adroplet containing a component forming material is discharged on aformation region of the component and solidified by baking, drying, andthe like to form a component having a desired pattern.

FIG. 15 shows one mode of a droplet discharge device used for a dropletdischarging method. Each of heads 1405 and 1412 of a droplet dischargemeans 1403 is connected to a control means 1407, and this control means1407 performs control a computer 1410 so that a preprogrammed patterncan be drawn. The drawing timing may be determined, for example, basedon a marker 1411 that is formed over a substrate 1400 as a reference.Alternatively, a reference point may be fixed based on an edge of thesubstrate 1400 as a reference. The reference point is detected by animaging means 1404, and then, detected data is changed into a digitalsignal by an image processing means 1409. Then, the digital signal isrecognized by the computer 1410 to generate a control signal, and thecontrol signal is transmitted to the control means 1407. An image sensoror the like using a charge coupled device (CCD) or a complementary metaloxide semiconductor (CMOS) can be used as the imaging means 1404.Naturally, information about a pattern to be formed over the substrate1400 is stored in a storage medium 1408, and the control signal istransmitted to the control means 1407 based on the information, so thateach of the heads 1405 and 1412 of the droplet discharge means 1403 canbe individually controlled. The heads 1405 and 1412 are supplied with amaterial to be discharged from material supply sources 1413 and 1414through pipes, respectively.

The head 1405 has an inside structure that has a space filled with aliquid material as shown by dotted lines 1406 and a nozzle that is adischarge opening. Although it is not illustrated, an inside structureof the head 1412 is similar to that of the head 1405. When the nozzlesizes of the heads 1405 and 1412 are different from each other,different materials with different widths can be dischargedsimultaneously. A conductive material, an organic material, an inorganicmaterial, and the like can also be respectively discharged from one headto draw a pattern. In a case of drawing in a wide area such as aninterlayer film, one material can be simultaneously discharged from aplurality of nozzles to improve throughput, and thus, drawing can beperformed. When a large-sized substrate is used, the heads 1405 and 1412can freely scan over the substrate in directions indicated by arrows,and a region to be drawn can be freely set. Thus, a plurality of thesame patterns can be drawn over one substrate.

In a case of forming a conductive layer by a droplet discharging method,a conductive layer is formed as follows: a composition containing aparticle shaped conductive material is discharged; and fusion, orwelding and joining is performed by baking to solidify the composition.A conductive layer (or an insulating layer) formed by discharging andbaking the composition containing the conductive material as describedabove tends to show a multi-crystalline state having many grainboundaries whereas a conductive layer (or an insulating layer) formed bysputtering tends to show a columnar structure.

Further, any structure may be used for a semiconductor layer included inthe transistors. For example, an impurity region (including a sourceregion, a drain region, and an LDD region) may be formed, and either ap-channel type or an n-channel type may be used. An insulating layer(sidewall) may be provided to be in contact with a side surface of thegate electrode, or a silicide layer may be formed in either or both ofthe source and drain regions, and the gate electrode. As a material forthe silicide layer, nickel, tungsten, molybdenum, cobalt, platinum, orthe like can be used.

As a material and a forming method of the first conductive layers 206 a,206 b, 256 a, 256 b, 286 a, and 286 b; and the second conductive layers213, 263, and 293 shown in the present embodiment mode, any one of thematerials and the forming methods shown in Embodiment Mode 1 can beemployed.

Further, the insulators 216, 266 a, 266 b, 296 a, and 296 b; and theorganic compound layers 212, 262 a, 262 b, and 292 can be provided byusing the similar material and forming method as the insulators and theorganic compound layers shown in the above Embodiment Mode 1.

In addition, a rectifying element may be provided between the firstconductive layers 206 a and 206 b and the organic compound layer 212;the first conductive layers 256 a and 256 b and the organic compoundlayers 262 a and 262 b, respectively; the first conductive layers 286 a,and 286 b and the organic compound layer 292, respectively. Therectifying element typically refers to a transistor or a diode in whicha gate electrode and a drain electrode are connected. For example, a PNjunction diode provided by stacking an n-type semiconductor layer and ap-type semiconductor layer can be used. In this manner, since a currentflows only in one direction by providing the rectifying diode, errorsare reduced and margin of reading is improved. In the case of providinga diode, not only a diode having a PN junction but also a diode havinganother structure such as a diode having a PIN junction or an avalanchediode may be provided. It is to be noted that the rectifying element maybe provided between the organic compound layer 212 and the secondconductive layer 213; the organic compound layers 262 a and 262 b andthe second conductive layer 263; and the organic compound layer 292 andthe second conductive layer 293, respectively.

In accordance with the memory element of the present invention,characteristics of a writing voltage of the memory element and the likeare stabilized without variation; therefore, normal writing in eachelement can be performed. Further, since a carrier injecting property isimproved by a tunnel current of the insulator, a film thickness of anorganic compound layer can be thickened. In addition, since a defectinside of a layer such as crystallization of an organic compound can beprevented due to a mixed layer of an insulator and an organic compound,condition of the organic compound layer is stabilized. Therefore, adefect in which the memory element is short-circuited in an initialstate before having conductivity can be prevented. As a result, a memorydevice and semiconductor device, each of which has high reliability, canbe provided with high yield.

Embodiment Mode 5

In the present embodiment mode, an example of a semiconductor devicethat includes the memory device shown in the above embodiment mode willbe described with reference to drawings.

A semiconductor device shown in the present embodiment mode is capableof reading and writing data without contact. A data transmission methodis broadly classified into three of an electromagnetic coupling methodof communicating by mutual induction with a pair of coils disposed inthe opposed position, an electromagnetic induction method ofcommunicating by an inductive electromagnetic field, and an electricwave method of communicating by using electric waves, and any of thesemethods may be employed. An antenna that is used for transmitting datacan be provided in two ways. One way is to provide the antenna over asubstrate provided with a plurality of elements and a memory element,and the other way is to provide a terminal portion over a substrateprovided with a plurality of elements and a memory element and toconnect an antenna provided over another substrate to the terminalportion.

First, an example of a structure of a semiconductor device in the caseof providing an antenna over a substrate provided with a plurality ofelements and a memory element will be described with reference to FIG.10.

FIG. 10 shows a semiconductor device including a memory device that hasan active matrix structure. A transistor part 330 including transistors310 a and 310 b, a transistor part 340 including transistors 320 a and320 b, and an element forming layer 335 including insulating layers 301a, 301 b, 308, 311, 316, and 314 are provided over a substrate 300. Amemory element portion 325 and a conductive layer 343 serving as anantenna are provided in the upper side of the element forming layer 335.

It is to be noted that, here, the case where the memory element portion325 or the conductive layer 343 serving as an antenna is provided in theupper side of the element forming layer 335 is shown; however, thepresent invention is not limited to this structure. It is possible toprovide the memory element portion 325 or the conductive layer 343serving as an antenna in the lower side of the element forming layer 335or in the same layer thereof.

The memory element portion 325 includes a memory element 315 a and amemory element 315 b. The memory element 315 a is formed by stacking apartition wall (insulating layer) 307 a, a partition wall (insulatinglayer) 307 b, an organic compound layer 312 including a plurality ofinsulators 326, and a second conductive layer 313 over a firstconductive layer 306 a. The memory element 315 b is provide by stackingthe partition wall (insulating layer) 307 b, a partition wall(insulating layer) 307 c, the organic compound layer 312 including aplurality of insulators 326, and the second conductive layer 313 over afirst conductive layer 306 b. Further, an insulating layer 314 servingas a protective film is formed to cover the second conductive layer 313.The first conductive layers 306 a and 306 b where the plurality ofmemory elements 315 a and 315 b are respectively formed are connected toa source electrode layer or a drain electrode layer of the transistors310 a and 310 b. In other words, each memory element is connected to onetransistor. The organic compound layer 312 including a plurality ofinsulators 326 is formed entirely to cover the first conductive layers306 a and 306 b; and the partition walls (insulating layers) 307 a, 307b, and 307 c. Alternatively, the organic compound layer 312 may beformed selectively in each memory cell. It is to be noted that thememory elements 315 a and 315 b can be formed by using the material orthe forming method described in the above embodiment mode.

Mixed condition of the insulators in the organic compound layer of thepresent embodiment mode is only an example. A concentration of theinsulators or the like can be arbitrarily controlled depending on aproperty or a size of a material used for an insulator, a material usedfor an organic compound and a conductive layer, and a forming method asshown in FIGS. 16A to 16C. For example, a concentration of insulatorsmay be gradually increased toward an interface of an organic compoundlayer and a first conductive layer and an interface of an organiccompound layer and a second conductive layer. Further, the concentrationmay be changed continuously or discontinuously in the organic compoundlayer.

In a memory device shown in FIG. 10 of the present embodiment mode, theorganic compound layer 312 including the insulator 326, which forms amemory element included in the memory device, is formed over the firstconductive layer. When a voltage is applied between the first conductivelayer and the second conductive layer, a current flows in the organiccompound layer 312, which generates heat (Joule heat). Then, when atemperature of the organic compound layer rises to a glass-transitiontemperature by Joule heat, a material forming the organic compound layer312 becomes a composition having fluidity. The composition havingfluidity flows without keeping a shape of a solid state. Therefore, afilm thickness of the organic compound layer is uneven, and the organiccompound layer is transformed. Then, the first conductive layer and thesecond conductive layer are connected to each other. As a result, thefirst conductive layer and the second conductive layer areshort-circuited. Therefore, conductivity of the memory element ischanged before and after applying a voltage.

A tunnel injection of carriers from the first conductive layer to theorganic compound layer 312 becomes possible due to the insulator 326existing at an interface of the organic compound layer 312 and the firstconductive layer. Therefore, characteristics of a writing voltage of thememory element and the like are stabilized without variation; therefore,normal writing in each element can be performed. Further, since aplurality of insulators are mixed in an organic compound layer, a defectsuch as crystallization of an organic compound can be prevented,condition of an organic compound layer is stabilized. In addition, sincea carrier injecting property is improved by the tunnel injection, a filmthickness of the organic compound layer can be thickened. Therefore, adefect in which the memory element is short-circuited in an initialstate before having conductivity can be prevented.

Further, the insulator 326 existing in the organic compound layer 312does not transport carriers. Therefore, a carrier transporting propertyof the entire organic compound layer 312 is reduced due to obstructionof the insulator 326. Thus, even in an organic compound material havinga high carrier transporting property, a current value that is necessaryfor short-circuit (writing into an element) is reduced to bring anadvantage such as low power consumption and expansion of selection rangeof a material.

In addition, in the memory element 315 a, a rectifying element may beprovided between the first conductive layer 306 a and the organiccompound layer 312 including the insulator 326, or between the organiccompound layer 312 including the insulator 326 and the second conductivelayer 313 as shown in the above embodiment mode. It is possible that therectifying element described above is used. It is to be noted that it isalso employed in the memory element 315 b.

Here, the conductive layer 343 serving as an antenna is provided over aconductive layer 342 that is formed of the same layer with the secondconductive layer 313. It is to be noted that a conductive layer servingas an antenna may be formed of the same layer with the second conductivelayer 313.

As a material of the conductive layer 343 serving as an antenna, anelement selected from gold (Au), platinum (Pt), nickel (Ni), tungsten(W), molybdenum (Mo), cobalt (Co), copper (Cu), aluminum (Al), manganese(Mn), and titanium (Ti) or an alloy containing a plurality of theelements can be used. Further, an evaporation method, sputtering, a CVDmethod, a dispenser method, any printing method such as gravure printingor screen printing, a droplet discharging method, or the like can beused to form the conductive layer 343 serving as an antenna.

Each of the transistors 310 a, 310 b, 310 c, and 310 d included in theelement forming layer 335 can be provided by a p-channel TFT or ann-channel TFT, or a CMOS circuit combining a p-channel TFT and ann-channel TFT. Further, any structure may be used for a semiconductorlayer included in the transistors 310 a, 310 b, 310 c, and 310 d. Forexample, an impurity region (including a source region, a drain region,and an LDD region) may be formed, and either a p-channel type or ann-channel type may be employed. An insulating layer (sidewall) may beformed to be in contact with a side face of the gate electrode, or asilicide layer may be formed for either or both of source and drainregions and the gate electrode. As a material for the silicide layer,nickel, tungsten, molybdenum, cobalt, platinum, or the like can be used.

Each of the transistors 310 a, 310 b, 310 c, and 310 d included in theelement forming layer 335 may be provided using an organic transistor inwhich a semiconductor layer forming the transistors is formed of anorganic compound. In this case, the element forming layer 335 includingthe organic transistor can be formed by using a direct printing method,a droplet discharging method, or the like over the substrate 300 that isa flexible substrate such as a plastic substrate. By using a printingmethod, a droplet discharging method, or the like, a semiconductordevice can be manufactured at low cost.

Further, the element forming layer 335, the memory elements 315 a, and315 b, and the conductive layer 343 serving as an antenna can be formedby an evaporation method, sputtering, a CVD method, a dispenser method,a droplet discharging method or the like as described above. It is to benoted that different methods may be employed to form different parts.For example, in order to obtain a transistor requiring high-speedoperation, a semiconductor layer formed of Si or the like is providedover a substrate and crystallized by a heat treatment, and then, atransistor serving as a switching element can be provided as an organictransistor in the upper side of a element forming layer by using aprinting method or a droplet discharging method.

It is to be noted that a sensor connecting to the transistor may beprovided. As the sensor, an element for detecting properties such astemperature, humidity, illuminance, gas, gravity, pressure, sound(vibration), and acceleration by a physical means or a chemical meanscan be given. The sensor can be formed by a semiconductor element suchas a resistance element, a capacitive coupling element, an inductivecoupling element, a photovoltaic element, a photoelectric conversionelement, a thermoelectromotive force element, a transistor, athermistor, or a diode.

Next, an example of a structure of a semiconductor device will bedescribed with reference to FIG. 11, in the case where the semiconductordevice is provided by providing a terminal portion over a substrateprovided with a plurality of elements and a memory element to connectwith an antenna provided over another substrate.

FIG. 11 shows a semiconductor device including a memory device that hasa passive matrix structure. An element forming layer 385 is providedover a substrate 350, and a memory element portion 375 is provided overthe element forming layer 385. A conductive layer 393 serving as anantenna is provided over a substrate 396 to connect to the elementforming layer 385. Here, the case where the memory element portion 375or the conductive layer 393 serving as an antenna is provide in theupper side of the element forming layer 385, is shown; however, thepresent invention is not limited to this structure. It is possible thatthe memory element portion 375 is provided in the lower side of theelement forming layer 385 or in the same layer thereof. Alternatively,it is also possible that the conductive layer 393 serving as an antennais provided in the lower side of the element forming layer 385.

The memory element portion 375 includes memory elements 365 a and 365 b.The memory element 365 a is formed by stacking a partition wall(insulating layer) 375 a, a partition wall (insulating layer) 375 b, anorganic compound layer 362 a including a plurality of insulators 376 a,and a second conductive layer 363 a over a first conductive layer 356.The memory element 365 b is formed by stacking the partition wall(insulating layer) 357 b, a partition wall (insulating layer) 357 c, anorganic compound layer 362 b including a plurality of insulators 376 b,and a second conductive layer 363 b over the first conductive layer 356.Further, an insulating layer 364 serving as a protective film is formedto cover the second conductive layers 363 a and 363 b. In addition, thefirst conductive layer 356 where a plurality of memory elements 365 aand 365 b are formed is connected to a source electrode layer or a drainelectrode layer of the only transistor 360 b. In other words, the memoryelements are connected to the one same transistor. The organic compoundlayer 362 a including the insulator 376 a and the organic compound layer362 b including the insulator 376 b provide the partition walls(insulating layers) 357 a, 357 b, and 357 c between each memory cell toisolate the insulating layers. However, when influence of electric fieldin lateral directions between each adjacent memory cell is notconcerned, the organic compound layers 362 a and 362 b may be formedover the entire surface of the first conductive layer 356. It is to benoted that the memory elements 365 a and 365 b can be formed by usingthe material and the manufacturing method shown in the above embodimentmode.

Mixed condition of the insulator in the organic compound layer of thepresent embodiment mode is only an example. A concentration of theinsulator or the like can be arbitrarily controlled depending on aproperty or a size of a material used for an insulator, a material usedfor an organic compound and a conductive layer, and a forming method asshown in FIGS. 16A to 16C. For example, a concentration of insulatorsmay be gradually increased toward an interface of an organic compoundlayer and a first conductive layer and an interface of an organiccompound layer and a second conductive layer. Further, the concentrationmay be changed continuously or discontinuously in the organic compoundlayer.

In the memory device shown in FIG. 11 of the present embodiment mode,the organic compound layer 362 a including the insulator 376 a and theorganic compound layer 362 b including the insulator 376 b, which form amemory element included in the memory device, is formed over the firstconductive layer. When a voltage is applied between the first conductivelayer and the second conductive layer, a current flows in the organiccompound layer 362 a and the organic compound layer 362 b, whichgenerates heat (Joule heat). Then, when a temperature of the organiccompound layer rises to a glass-transition temperature by Joule heat, amaterial forming the organic compound layer 362 a and the organiccompound layer 362 b becomes a composition having fluidity. Thecomposition having fluidity flows without keeping a shape of a solidstate. Therefore, a film thickness of the organic compound layer isuneven, and the organic compound layer is transformed. Then, the firstconductive layer and the second conductive layer are connected with eachother. As a result, the first conductive layer and the second conductivelayer are short-circuited. Therefore, conductivity of the memory elementis changed before and after applying a voltage.

A tunnel injection of carriers from the first conductive layer to theorganic compound layer 362 a and the organic compound layer 362 bbecomes possible due to the insulator 376 a and the insulator 376 b eachexisting at an interface of the organic compound layer 362 a and thefirst conductive layer and an interface of the organic compound layer362 b and the first conductive layer. Therefore, characteristics of awriting voltage of the memory element and the like are stabilizedwithout variation; therefore, normal writing in each element can beperformed. Further, since a plurality of insulators are mixed in anorganic compound layer, a defect inside of a layer such ascrystallization of an organic compound can be prevented from generating,and condition of an organic compound layer is stabilized. In addition,since a carrier injecting property is improved by the tunnel injection,a film thickness of the organic compound layer can be thickened.Therefore, a defect in which the memory element is short-circuited in aninitial state before having conductivity can be prevented.

Further, the insulator 376 a and the insulator 376 b each existing inthe organic compound layer 362 a and the organic compound layer 362 bdoes not transport carriers. Therefore, a carrier transporting propertyof the entire organic compound layers 362 a and 362 b is reduced due toobstruction of the insulators 376 a and 376 b. Thus, even in an organiccompound material having a high carrier transporting property, a currentvalue that is necessary for short-circuit (writing into an element) isreduced to bring an advantage such as low power consumption andexpansion of selection range of a material.

The substrate including the element forming layer 385 and the memoryelement portion 375 is attached to the substrate 396 provided with theconductive layer 393 serving as an antenna with an adhesive resin 395.The element forming layer 385 and the conductive layer 393 areelectrically connected to each other through conductive fine particles394 contained in the resin 395. Alternatively, the substrate includingthe element forming layer 385 and the memory element portion 375 may beattached to the substrate 396 provided with the conductive layer 393serving as an antenna with a conductive adhesive such as silver paste,copper paste, or carbon paste, or by solder bonding.

Thus, a semiconductor device provided with a memory device and anantenna can be formed. In addition, in the present embodiment mode, anelement forming layer can be provided by forming a thin film transistorover a substrate. Alternatively, a semiconductor substrate such as a Sisubstrate is used as a substrate, and an element forming layer may beprovided by forming a filed effect transistor over the substrate.Furthermore, an SOI substrate may be used as a substrate and an elementforming layer may be provided thereover. In this case, the SOI substratemay be formed by attaching wafers or by using a method called SIMOX inwhich an insulating layer is formed inside a substrate by implantingoxygen ions into a Si substrate.

In addition, a memory element portion may be provided over a substrateprovided with a conductive layer serving as an antenna. Further, asensor connecting to a transistor may be provided.

It is to be noted that the present embodiment mode can be freelycombined with the above embodiment modes. Further, the semiconductordevice manufactured in the present embodiment mode is separated from thesubstrate by a separation process and is attached to a flexiblesubstrate to be provided over a flexible substratum. Then, asemiconductor device having flexibility can be obtained. The flexiblesubstratum corresponds to a film made of polypropylene, polyester,vinyl, polyvinyl fluoride, polyvinyl chloride, or the like, paper madefrom a fibrous material, a stacked film of a base film (polyester,polyamide, an inorganic vapor deposition film, paper, or the like) andan adhesive synthetic resin film (an acrylic-based synthetic resin, anepoxy-based synthetic resin, or the like), or the like. The films aresubjected to a heat treatment and a pressure treatment bythermocompression bonding. An adhesive layer that is provided on theoutermost surface of the layer, or a layer (not an adhesive layer) thatis provided on the outermost layer thereof, is melted by a hearttreatment, and then is pressured, so that the films are attached. Anadhesive layer may be provided on the substratum or it may not beprovided. The adhesive layer corresponds to a layer containing anadhesive such as a heat curable resin, an ultraviolet-curable resin, anepoxy resin-based adhesive, or a resin additive.

In accordance with the memory element of the present invention,characteristics of a writing voltage of the memory element and the likeare stabilized without variation; therefore, normal writing in eachelement can be performed. Further, since a carrier injecting property isimproved by a tunnel current of a mixed layer of an inorganic insulatorand an organic compound, a film thickness of an organic compound layercan be thickened. Therefore, a defect in which the memory element isshort-circuited in an initial state before having conductivity can beprevented. As a result, a memory device and a semiconductor device, eachof which has high reliability, can be provided with high yield.

Embodiment Mode 6

In the present embodiment, reading or writing date into thesemiconductor device having the above structure will be described.

Writing data into the semiconductor device having the above structurecan be performed by adding electric action. The case of writing data byadding electric action will be described (FIG. 3).

When writing data is performed by adding electric action, one of memorycells 721 is selected by a row decoder 724 a, a column decoder 726 a,and a selector 726 c, and then, data is written into the memory cell 721with the use of a writing circuit. Specifically, a large voltage isselectively applied to an organic compound layer 752 in a desiredportion, and a large amount of current is fed so that short-circuit iscaused between a first conductive layer 751 b and a second conductivelayer 753 b.

Electric resistance of the short-circuited portion is largely decreasedcompared to that of the other portions. Thus, by adding the electricaction, writing data is performed by utilizing a change in the electricresistance between the two conductive layers. For example, in the casewhere an organic compound layer to which the electric action is notadded, is used as data “0”, when writing data “1”, a large voltage isselectively applied to the organic compound layer in a desired portion,and a large amount of current is fed to cause short-circuit and todecrease the electric resistance.

Subsequently, operation in the case of reading data from a memoryelement will be described (see FIG. 9). Here, a reading circuit 726 bincludes a resistance element 746 and a sense amplifier 747. However,the reading circuit 726 b is not limited to the above structure, and thereading circuit may have any structure.

Reading data is performed by applying a voltage between the firstconductive layer 751 b and the second conductive layer 753 b to a readelectric resistance value of an organic compound layer 752. For example,in the case of writing the data by applying electric action as describedabove, a resistance value Ra1 in the case where the electric action isnot added, and a resistance value Rb1 in the case where the electricvalue is added so that short-circuit is caused between the twoconductive layers, fulfill Ra1>Rb1. Reading data is performed byelectrically reading such a difference in the resistance value.

For example, data of the memory cell 721 disposed in an x-th column anda y-th row is read among a plurality of the memory cells 721 included ina memory cell array 722. In that case, first, a bit line Bx in the x-thcolumn and a word line Wy in the y-th row are selected by the rowdecoder 724 a, the column decoder 726 a, and the selector 726 c. Then,an organic compound layer included in the memory cell 721 and aresistance element 746 are in such a state that they are connected inseries. Thus, a voltage is applied to the opposite edges of the twoconnected resistance elements in series, electric potential of a node αbecomes resistance-divided electric potential in accordance with theresistance value Ra or Rb of the organic compound layer 752. Theelectric potential of the node α is supplied to a sense amplifier 747.In the sense amplifier 747, which of the information “0” and “1” iscontained is judged. After that, a signal containing the information “0”or “1” judged by the sense amplifier 747 is supplied to the outside.

In accordance with the above method, the state of the electricresistance in the organic compound layer is read by a voltage valueutilizing the difference in the resistance value and the resistancedivision. However, a method in which current values are compared may beemployed. This method, for example, utilizes that a current value Ia1 inthe case where the electric action is not added to the organic compoundlayer, and a resistance value Ib1 in the case where the electric actionis added to the organic compound layer so that short-circuit is causedbetween the two conductive layers, fulfill Ia1<Ib1. Thus, reading datamay be performed by electrically reading such a difference in thecurrent value.

Since a memory element having the above structure and a semiconductordevice provided with the memory element are nonvolatile memories, anelectric battery for storing data is not required to be mounted. Asmall-sized, thin, and lightweight semiconductor device can be provided.Further, by using the insulating material that is used in the aboveembodiment mode as an organic compound layer, rewriting data cannot beperformed though writing data (additionally) is possible. Accordingly,counterfeits can be prevented and a semiconductor device with ensuredsecurity can be provided.

It is to be noted that a memory element having a passive matrixstructure of which a memory circuit is a simple and semiconductor deviceprovided with the memory element have been taken as examples in thepresent embodiment mode. However, even in the case of using a memorycircuit having an active matrix structure, data can be written or readin a similar manner.

Here, in the case of an active matrix structure, a specific example ofreading data in a memory element by electric action will be describedwith reference to FIGS. 14A and 14B.

FIGS. 14A and 14B show current-voltage characteristics 951 of a memoryelement portion in which data “0” is written, current-voltagecharacteristics 952 a memory element portion of in which data “1” iswritten, and current-voltage characteristics 953 of a resistance element246. Here, the case of using a transistor as the resistance element 246is shown. In addition, the case of applying 3 V between a firstconductive layer 243 and a second conductive layer 245 as a operationvoltage in reading data will be described.

In FIGS. 14A and 14B, as for a memory cell having a memory elementportion in which data “0” is written, an intersection point 954 of thecurrent-voltage characteristics 951 of the memory element portion andthe current-voltage characteristics 953 of the transistor is anoperational point, and potential of a node α at this time is V1 (V). Thepotential of the node α is supplied to a sense amplifier 247. The datastored in the memory cell is recognized as “0” in the sense amplifier247.

Meanwhile, as for a memory cell having a memory element portion in whichdata “1” is written, an intersection point 955 of the current-voltagecharacteristics a memory element portion 952 of and the current-voltagecharacteristics 953 of the transistor is an operational point, andpotential of a node α at this time is V2 (V) (V1>V2). The potential ofthe node α is supplied to the sense amplifier 247. The data stored inthe memory cell is recognized as “1” in the sense amplifier 247.

Thus, the data stored in the memory cell can be distinguished by readingthe potential divided by resistance in accordance with the resistancevalue of a memory element portion 241.

It is to be noted that the present embodiment mode can be freelycombined with any structures of the memory element and the semiconductordevice provided with the memory element shown in the above embodimentmodes.

Embodiment Mode 7

A structure of a semiconductor device of the present embodiment modewill be described with reference to FIG. 12A. As shown in FIG. 12A, asemiconductor device 20 of the present invention has a function ofcommunicating data without contact, and includes a power supply circuit11, a clock generation circuit 12, a data demodulation/modulationcircuit 13, a control circuit 14 for controlling other circuits, aninterface circuit 15, a memory circuit 16, a data bus 17, an antenna(antenna coil) 18, a sensor 21, and a sensor circuit 22.

In the power supply circuit 11, various kinds of power supplies, whichare supplied to each circuit in the semiconductor device 20, aregenerated in accordance with an alternating current signal inputted fromthe antenna 18. In the clock generation circuit 12, various kinds ofclock signals, which are supplied to each circuit in the semiconductordevice 20, are generated in accordance with an alternative currentsignal inputted from the antenna 18. The data demodulation/modulationcircuit 13 has a function of demodulating/modulating data communicatedwith a reader/writer 19. The control circuit 14 has a function ofcontrolling the memory circuit 16. The antenna 18 has a function oftransmitting/receiving electromagnetic fields or electric waves. Thereader/writer 19 communicates with the semiconductor device, andcontrols a process with regard to the data of the semiconductor device.It is to be noted that the structure of the semiconductor device is notlimited to the above structure, and, for example, other elements such asa limiter circuit of a power supply voltage and hard ware dedicated toencryption may be additionally provided.

The memory circuit 16 has a memory element where an organic compoundlayer or a phase change layer is interposed between a pair of conductivelayers. It is to be noted that the memory circuit 16 may have only thememory element where an organic compound layer or a phase change layeris interposed between a pair of conductive layers, or may have anothermemory circuit with a different structure. The memory circuit with adifferent structure corresponds, for example, to one or more selectedfrom a DRAM, an SRAM, an FeRAM, a mask ROM, a PROM, an EPROM, an EEPROM,and a flash memory.

The sensor 21 is formed using a semiconductor element such as aresistance element, a capacitive coupling element, an inductive couplingelement, a photovoltaic element, a photoelectric conversion element, athermal electromotive force element, a transistor, a thermistor, and adiode. The sensor circuit 22 detects changes in impedance, reactance,inductance, a voltage, or a current, and performs analog/digital (A/D)conversion to output a signal to the control circuit 14.

Embodiment Mode 8

In accordance with the present invention, a semiconductor device servingas a processor chip (also referred to as a wireless chip, a wirelessprocessor, a wireless memory, and a wireless tag) can be formed. Theusage of the semiconductor device of the present invention iswide-ranging. For example, the semiconductor device can be used by beingprovided on paper money, coin, securities, certificates, bearer bonds,packing containers, documents, recording medium, personal belongings,vehicles, foods, garments, health articles, livingwares, medicines,electronic apparatuses, and the like.

The paper money and coins are money distributed in the market andinclude currency (cash vouchers) available in a certain area in asimilar way to money, and memorial coins and the like. The securitiesrefer to checks, stock certificates, promissory notes, and the like,which can be provided with a processor chip 90 (see FIG. 13A). Thecertificates refer to driver's licenses, certificates of residence, andthe like, which can be provided with a processor chip 91 (see FIG. 13B).The personal belongings refer to a bag, a pair of glasses, and the like,which can be provided with a processor chip 97 (see FIG. 13C). Thebearer bonds refer to stamps, rice coupons, various merchandise coupons,and the like. The packing containers refer to wrapping paper for a boxlunch, plastic bottles, and the like, which can be provided with aprocessor chip 93 (see FIG. 13D). The documents refer to volumes, booksand the like, which can be provided with a processor chip 94 (see FIG.13E). The recording medium refer to DVD software, video tapes, and thelike, which can be provided with a processor chip 95 (see FIG. 13F). Thevehicles refer to wheeled vehicles such as bicycles, vessels, and thelike, which can be provided with a processor chip 96 (FIG. 13G). Thefoods refer to eatables, drinks, and the like. The garments refer toclothes, chaussures, and the like. The health articles refer to medicalappliances, health appliances, and the like. The livingwares refer tofurniture, lighting equipment, and the like. The medicines refer tomedical products, pesticides, and the like. The electronic apparatusesrefer to liquid crystal display apparatuses, EL display apparatuses,television apparatuses (TV sets or flat-screen televisions), cellularphones, and the like.

The semiconductor device of the present invention is fixed to productsby mounting the device onto a print substrate, pasting the device to thesurface, or embedding the device in the products. For example, thesemiconductor device is embedded in a paper of a book or in organicresin of a package made from the organic resin. Since the semiconductordevice of the present invention is realized to be small, thin, andlightweight, design of a product is not detracted after fixating thesemiconductor device to the product. A certification function can beprovided by providing the semiconductor device to the paper money, thecoins, the securities, the bearer bonds, the certificates, and the like.A counterfeit can be prevented by employing the certification function.The efficiency in an inspection system can be promoted by providing thesemiconductor device to the packing containers, the recording medium,the personal belongings, the foods, the garments, the livingwares, theelectronic apparatuses, and the like.

Next, a mode of an electronic apparatus where the semiconductor deviceof the present invention is mounted is described with reference to thedrawings. The electronic apparatus shown here is a cellular phone, whichincludes frame bodies 2700 and 2706, a panel 2701, a housing 2702, aprinted circuit board 2703, operation switches 2704, and a battery 2705(see FIG. 12B). The panel 2701 is detachably incorporated in the housing2702. The housing 2702 is fitted into the printed circuit board 2703. Ashape and dimension of the housing 2702 are appropriately changed inaccordance with the electronic apparatus where the panel 2701 is to beincorporated. Over the printed circuit board 2703, a plurality ofpackaged semiconductor devices are mounted and the semiconductor deviceof the present invention can be used as one of the plurality of packagedsemiconductor devices. The plurality of semiconductor devices mountedonto the printed circuit board 2703 has any one of functions of acontroller, a central processing unit (CPU), a memory, a power supplycircuit, an audio processing circuit, a transmitting/receiving circuit,and the like.

The panel 2701 is combined with the printed circuit board 2703 through aconnection film 2708. The above panel 2701, the housing 2702, and theprinted circuit board 2703 are placed in the frame bodies 2700 and 2706together with the operation switches 2704 and the battery 2705. A pixelregion 2709 in the panel 2701 is provided so as to be observed throughan opening window provided in the frame body 2700.

As described above, the semiconductor device of the present invention issmall, thin, and lightweight, whereby the limited space in the framebodies 2700 and 2706 of the electric apparatus can be efficiency used.

Further, since the semiconductor device of the present inventionincludes a memory element having a simple structure in which an organiccompound layer is interposed between a pair of conductive layers, anelectric apparatus using an inexpensive semiconductor device can beprovided. In addition, since high integration is easy with thesemiconductor device of the present invention, an electric apparatususing a semiconductor device including a high-capacity memory circuitcan be provided.

Further, a memory device in the semiconductor device of the presentinvention is nonvolatile and additionally recordable, and the data iswritten in the memory device by electric action. With thischaracteristic, the counterfeiting due to the rewriting can be preventedand new data can be additionally written. Therefore, an electricapparatus using a sophisticated and high-value-added semiconductordevice can be provided.

It is to be noted that the frame bodies 2700 and 2706 are shown as anexample of an exterior of the cellular phone, and the electric apparatusof the present embodiment mode can be changed variously in accordancewith the function or the intended purpose thereof.

Embodiment Mode 9

In the present embodiment mode, reading or writing data in asemiconductor device having the above structure will be described.

FIGS. 18A to 18C show a configuration example of a semiconductor deviceof the present invention. The semiconductor device includes a memorycell array 1722 in which memory cells 1721 are arranged in matrix, acircuit 1726 having a reading circuit and a writing circuit, a decoder1724, and a decoder 1723. It is to be noted that the configuration of amemory device 1716 shown here is only an example, and a semiconductordevice may include another circuit such as a sense amplifier, an outputcircuit, a buffer, and an interface that communicates with outside.

The memory cell 1721 includes a first conductive layer that is connectedto a bit line Bx (1≦x≦m), a second conductive layer that is connected toa word line Wy (1≦y≦n), and an organic compound layer. The organiccompound layer has a single layer structure or a stacked layer structurebetween the first conductive layer and the second conductive layer.

First, operation of writing data into a memory element in a memorydevice having a passive matrix structure is described with references toFIGS. 18A to 18C. Data is written by electric action. Therefore, thecase of writing data by electric action is firstly described. Writing isperformed by changing electric characteristics of a memory cell, and aninitial state (a state without electric action) of the memory cell isused as data “0” and a state in which electric characteristics ischanged is used as data “1”.

In the case of writing data “1” into the memory cell 1721, the memorycell 1721 is selected first by the decoders 1723 and 1724 and a selector1725. Specifically, a predetermined voltage V2 is applied to a word lineW3 connected to the memory cell 1721 by the decoder 1724. A bit line B3connected to the memory cell 1721 is connected to a circuit 1726 by thedecoder 1723 and the selector 1725. Then, a writing voltage V1 isoutputted from the circuit 1726 to the bit line B3. Thus, electricpotential Vw=V1−V2 is applied between the first conductive layer and thesecond conductive layer included in the memory cell 1721. By selectingappropriate electric potential Vw, an organic compound layer providedbetween the conductive layers is changed physically or electrically towrite data “1”. Specifically, at a reading operation voltage, electricresistance between the first conductive layer and second conductivelayer in the state of data “1” may be changed so as to be drasticallylowered compared with the electric resistance in the state of data “0”.For example, the voltage may be appropriately selected from the range of(V1, V2)=(0 V, 5 V to 15 V) or (3 V to 5 V, −12 V to −2 V). The electricpotential Vw may be 5V to 15V or −5V to −15V.

A non-selected word line and a non-selected bit line are controlled sothat data “1” is not written into the memory cell that is to beconnected to the non-selected word line and the non-selected bit line.For example, the non-selected word line and the non-selected bit linemay be in a floating state. Characteristics that can ensure selectivitysuch as diode characteristics are required between the first conductivelayer and second conductive layer included in the memory cell.

On the other hand, in the case of writing data “0” into the memory cell1721, electric action is not required to be applied to the memory cell1721. In circuit operation, for example, the memory cell 1721 isselected by the decoders 1723 and 1724 and the selector 1725 in thesimilar way as the case of writing data “1”. Then, the output electricpotential from the circuit 1726 to the bit line B3 may be set to beequivalent to electric potential of a selected word line W3 or electricpotential of a non-selected word line, and such a voltage (for example,−5 V to 5 V) that does not change the electric characteristics of thememory cell 1721 may be applied between the first conductive layer andsecond conductive layer included in the memory cell 1721.

Subsequently, operation of reading data from a memory element in amemory device having passive matrix structure is described (see FIGS.18A to 18C). Reading data is performed by utilizing electriccharacteristics between a first conductive layer and a second conductivelayer included in a memory cell, which are different between a memorycell having data “0” and a memory cell having data “1”. For example, areading method utilizing the difference in electric resistance isdescribed, where the effective electric resistance between a firstconductive layer and a second conductive layer included in a memory cell(hereinafter also simply referred to as electric resistance of thememory cell) with data “0” is R0 at a reading voltage, and the electricresistance of a memory cell with data “1” is R1 at a reading voltage(R1<<R0). As for a reading/writing circuit, for example, a circuit 1726using a resistance element 1746 and a differential amplifier 1747 shownin FIG. 18B can be conceivable as a structure of its reading portion.The resistance element 1746 has a resistance value Rr (R1<Rr<R0). Atransistor 1748 may be used instead of the resistance element 1746 and aclocked inverter 1749 can be used instead of the differential amplifier(FIG. 18C). A signal φ or an inverted signal φ that is Hi when readingis performed and Lo when reading is not performed is inputted into theclocked inverter 1749. Naturally, the circuit configuration is notlimited to FIGS. 18A to 18C.

In the case of reading data from the memory cell 1721, the memory cell1721 is selected first by the decoders 1723 and 1724 and the selector1725. Specifically, a predetermined voltage Vy is applied to a word lineWy connected to the memory cell 1721 by the decoder 1724. A bit line Bxconnected to the memory cell 1721 is connected to a terminal P of thecircuit 1726 by the decoder 1723 and the selector 1725. As a result,electric potential Vp of the terminal P is a value determined byresistance division by the resistance element 1746 (resistance value:Rr) and the memory cell 1721 (resistance value: R0 or R1). Therefore,the equation Vp0=Vy+(V0−Vy)×R0/(R0+Rr) is made in the case where thememory cell 1721 has data “0”. Alternatively, the equationVp1=Vy+(V0−Vy)×R1/(R1+Rr) is made in the case where the memory cell 1721has data “1”. As a result, by selecting Vref so as to be between Vp0 andVp1 in FIG. 18B or by selecting the change point of the clocked inverterbetween Vp0 and Vp1 in FIG. 18C, output electric potential Vout of Lo/Hi(or Hi/Lo) is outputted in accordance with data “0”/“1”, so that readingcan be performed.

For example, it is assumed that the differential amplifier is operatedat Vdd=3 V, and Vy, V0, and Vref are 0 V, 3 V, and 1.5 V, respectively.On the condition of R0/Rr=Rr/R1=9, Hi is outputted as Vout in accordancewith Vp0=2.7 V when the memory cell has data “0”, or Lo is outputted asVout in accordance with Vp1=0.3 V when a memory cell has data “1”. Inthis way, reading of a memory cell can be performed.

In accordance with the above method, the state of electric resistance ofan organic compound layer is read at a voltage value utilizing thedifference in a resistance value and resistance division. Naturally, thereading method is not limited thereto. For example, reading may beperformed utilizing the different in current values other than utilizingthe difference in electric resistant. In the case where electriccharacteristics of the memory cell have different diode characteristicsbetween threshold voltages in the case of data “0” and data “1”, readingmay be performed utilizing the difference in the threshold voltage.

Next, operation of writing data into a memory element in a memory devicehaving an active matrix structure is described (see FIGS. 19A to 19C).

FIGS. 19A to 19C show a configuration example of a memory device shownin the present embodiment mode. The memory device includes a memory cellarray 1232 in which memory cells 1231 are arranged in matrix, a circuit1226, a decoder 1224, and a decoder 1223. The circuit 1226 has a readingcircuit and a writing circuit. It is to be noted that the configurationof a memory device 1217 shown here is only an example, and a memorydevice may include another circuit such as a sense amplifier, an out putcircuit, a buffer, and an interface that communicates with outside.

The memory cell array 1232 includes a first wiring that is connected toa bit line Bx (1≦x≦m), a second wiring that is connected to a word lineWy (1≦y≦n), a transistor 1210 a, a memory element 1215 b, and the memorycell 1231. The memory element 1215 b has a structure in which an organiccompound layer is interposed between a pair of conductive layers. A gateelectrode of the transistor is connected to the word line. Either asource electrode or a drain electrode is connected to the bit line, andthe other electrode is connected to one of two terminals included in thememory element. The other terminal of the memory element is connected toa common electrode (electric potential, Vcom).

First, operation of writing data by electric action is described. It isto be noted that writing is performed by changing electriccharacteristics of the memory cell, and an initial state (a statewithout electric action) of the memory cell is data “0” and a state inwhich the electric characteristics is changed is data “1”.

Here, the case of writing data into the memory cell 1231 in the n-th rowand m-th column is described. In the case of writing data “1” into thememory cell 1231, the memory cell 1231 is selected first by the decoders1223 and 1224 and the selector 1225. Specifically, a predeterminedvoltage V22 is applied to a word line Wn connected to the memory cell1231 by the decoder 1224. In addition, a bit line Bm connected to thememory cell 1231 is connected to the circuit 1226 having a readingcircuit and a writing circuit by the decoder 1223 and the selector 1225.Then, a writing voltage V21 is outputted from the circuit 1226 into abit line B3.

In this manner, a transistor 1210 a included in the memory cell isturned on, and the memory element 1215 b is electrically connected tothe bit line to apply electric potential (voltage) of approximatelyVw=Vcom−V21. It is to be noted that one of electrodes of the memoryelement 1215 b is connected to a common electrode of which electricpotential is Vcom. An organic compound layer provided between theconductive layers is changed physically or electrically by appropriatelyselecting the electric potential Vw so that data “1” is written.Specifically, in a reading operation voltage, electric resistancebetween the first conductive layer and second conductive layer in thestate of data “1” may be changed so as to be drastically loweredcompared with the electric resistance in the state of data “0”, orsimply, short circuit may be caused. The electrical potential may beappropriately selected from the range of (V21, V22, Vcom)=(5 V to 15V, 5V to 15 V, 0 V) or (−12 V to 0 V, −12 V to 0 V, 3 V to 5 V). Theelectric potential Vw may be 5 V to 15 V or −5 V to −15 V.

A non-selected word line and a non-selected bit line are controlled sothat data “1” is not written into a memory cell that is to be connectedto each of the non-selected word line and the non-selected bit line.Specifically, electric potential (for example, 0 V) for turning off thetransistor in the memory cell that is to be connected may be applied tothe non-selected word line, and the non-selected bit line may be in afloating state or electric potential appropriately equivalent to Vcommay be applied to the non-selected bit line.

On the other hand, in the case of writing data “0” into the memory cell1231, electric action is not required to be applied to the memory cell1231. In circuit operation, for example, although the memory cell 1231is selected by the decoders 1223 and 1224 and the selector 1225 in thesimilar way as the case of writing data “1”, an output electricpotential from the circuit 1226 to the bit line B3 is set to beequivalent to the Vcom or the bit line B3 is set to be in a floatingstate. As a result, low electric potential (for example, −5 V to 5 V) orno electric potential (no voltage) is applied; therefore, electriccharacteristics are not changed and writing data “0” is realized.

Next, operation of reading data by electric action is described. Here,the circuit 1226 has a configuration including a resistance element 1246and a different amplifier 1247. However, a configuration of the circuit1226 is not limited to the above, and any configuration may be employed.

Subsequently, operation of reading data by electric action in a memorydevice that has an active matrix structure is described. Reading data isperformed by utilizing electric characteristics of the memory element1215 b, which are different between a memory cell with data “0” and amemory cell with data “1”. For example, a reading method by utilizingthe difference in electric resistance is described, where electricresistance of the memory element included in the memory cell with data“0” is R0 at a reading voltage, and electric resistance of the memoryelement included in the memory cell with data “1” is R1 at a readingvoltage (R1<<R0). As for a reading/writing circuit, for example, thecircuit 1226 using the resistance element 1246 and the differentamplifier 1247 shown in FIG. 19B is conceivable as a structure of itsreading portion. The resistance element has a resistance value of Rr(R1<Rr<R0). A transistor 1249 may be used instead of the resistanceelement 1246 and a clocked inverter 1248 can be used instead of thedifferent amplifier (FIG. 19C). Naturally, a circuit configuration isnot limited to FIGS. 19A to 19C.

In the case of reading data from the memory cell 1231 in the x-th rowand the y-th column, the memory cell 1231 is selected first by thedecoders 1223 and 1224 and the selector 1225. Specifically, apredetermined voltage V24 is applied to a word line Wy connected to thememory cell 1231 by the decoder 1224 to turn on a transistor 1210 a. Inaddition, a bit line Bx connected to the memory cell 1231 is connectedto a terminal P of the circuit 1226 by the decoder 1223 and the selector1225. As a result, electric potential Vp of the terminal P is a valuedetermined by resistance division of Vcom and V0 by the resistanceelement 1246 (a resistance value: Rr) and the memory element 1215 b (aresistance value: R0 or R1). Therefore, the equationVp0=Vcom+(V0−Vcom)×R0/(R0+Rr) is made in the case where the memory cell1231 has data “0”. Alternatively, the equationVp1=Vcom+(V0−Vcom)×R1/(R1+Rr) is made in the case where the memory cell1231 has data “1”. As a result, by selecting Vref so as to be betweenVp0 and Vp1 in FIG. 19B or by selecting the change point of the clockedinverter so as to be between Vp0 and Vp1 in FIG. 19C, Lo/Hi (or Hi/Lo)of output electric potential Vout is outputted in accordance with data“0”/“1” so that reading can be performed.

For example, the differential amplifier is operated at Vdd=3 V, andVcom, V0, and Vref are 0 V, 3 V, and 1.5 V, respectively. On thecondition that the equation R0/Rr=Rr/R1=9 holds and on-resistance of thetransistor 1210 a can be ignored, Hi is outputted as Vout at Vp0=2.7 Vwhen a memory cell has data “0”, or Lo is outputted as Vout at Vp1=0.3 Vwhen a memory cell has data “1”. In this way, reading from a memory cellcan be performed.

In accordance with the above method, reading is performed by a voltagevalue utilizing the difference in a resistance value of the memoryelement 1215 b and resistance division. Naturally, the reading method isnot limited thereto. For example, reading may be performed by utilizingthe difference in current values other than the method utilizing thedifference in electric resistance. In the case where electriccharacteristics of the memory cell have different diode characteristicsin threshold voltages in the case of data “0” and data “1”, reading maybe performed by utilizing difference in the threshold voltages.

A memory element having the above structure and a memory deviceincluding the memory element are a nonvolatile memory; therefore, anelectric battery for storing data is not required to be incorporated,and a small-sized, thin, and lightweight memory device and asemiconductor device thereof can be provided. Further, by using theinsulating material used in the above embodiment modes as an organiccompound layer, data cannot be rewritten though data can be written(additionally). Accordingly, counterfeits can be prevented and a memorydevice and a semiconductor device with ensured security can be provided.

It is to be noted that the present embodiment mode can be performedfreely by combining the memory element, and the structure of the memorydevice and the semiconductor device, which include the memory elementshown in the above embodiment mode.

Embodiment

In the present embodiment, a memory element using the present inventionis manufactured, and an example of evaluating characteristics thereof isshown.

First, memory elements that do not have an insulator (sample 1 to sample3) as a comparative example are manufactured, and a writing voltage anda current value just before writing are measured. As a structure of thememory elements of the samples 1 to 3, a stacked layer structure of afirst conductive layer, an organic compound layer, and a secondconductive layer is employed. A titanium film with a film thickness of100 nm as the first conductive layer and an NPB film with a filmthickness of 8 nm as the organic compound layer are stacked, and then,an aluminum film with a film thickness of 200 nm as the secondconductive layer is formed thereover. The samples 1 to 3 are memoryelements of which shapes are squares. Each of the samples 1 and 2 is amemory element having a square shape of which length of one side is 10μm, and the sample 3 is a memory element having a square shape of whichlength of one side is 20 μm. In the present specification, a memoryelement is a stacked layer region including at least one of a firstconductive layer, an organic compound layer, and a second conductivelayer. In addition, a shape of the memory element is a shape of itsstacked body. Each writing voltage and current of the sample 1, thesample 2, and the sample 3 is shown in FIG. 20A, FIG. 20B, and FIG. 20C,respectively. It is to be noted that, as a writing method in this case,sweep measure by which a current value of the samples in each voltage ismeasured with increasing a voltage by every 0.1 V from 0 V, isperformed.

Although the memory elements of the sample 1 and the sample 2 in FIGS.20A and 20B have the same structure and the same size, characteristicsof a writing voltage and a current (also called I-V characteristics) isdifferent from each other, and there is no consistency. Therefore,variation in writing conduct among similar memory elements is generated.Furthermore, even if the memory elements are compared to an element inFIG. 20C showing I-V characteristics of the sample 3, which has thedifferent size of 20 μm×20 μm, writing conduct of the sample 1 and thesample 2 shown in FIGS. 20A and 20B has no consistency, and there isvariation.

FIG. 21 shows a cross-sectional view of a memory element after writing(a sample 4) (a STEM photograph observed by a transmission electronmicroscopy (TEM) method). The memory element of the sample 4 shown inFIG. 21 is formed of a stacked layer of a titanium film 30 that is abottom electrode layer, an NPB film 31 that is an organic compoundlayer, and an aluminum film 32 that is an upper electrode layer.Further, a partition wall 34 and an aluminum film 33 are formed on itsperiphery.

As shown in FIG. 21, the aluminum film that is an upper electrode layeris broken due to a concentration of electricity. There is a possibilitythat short-circuit between an upper electrode and a bottom electrode iscaused on the periphery of the broken aluminum. Heat and a charge aregenerated when the upper electrode layer is broken; then, the shapes ofthe partition wall 34 and the titanium film 30 that is the bottomelectrode are affected due to the heat and the charge. Therefore, theshapes are changed.

On the other hand, a memory element having an insulator as the presentinvention is manufactured, and a writing voltage and a current aremeasured. As a sample, samples (a sample 5 and a sample 6) having astacked layer structure of a first conductive layer (a titanium film),an insulating layer (a lithium fluoride film with a film thickness of 1nm), an organic compound layer (an NPB film with a film thickness of 10nm), and a second conductive layer (an aluminum film), in which aninsulator is provided as a buffer layer in a thin film state, aremanufactured. Samples (a sample 7 and a sample 8) having a stacked layerstructure of a first conductive layer (a titanium film), an organiccompound (NPB) layer including an insulator (lithium fluoride) (a filmthickness of 20 nm) (a volume ratio of lithium fluoride and NPB is 1:1),and a second conductive layer (an aluminum film), in which an insulatoris mixed in an organic compound as the present invention, are alsomanufactured. In the sample 5 and the sample 7, a size of each memoryelement is 2 μm×2 μm. In the sample 6 and the sample 8, a size of eachmemory element is 3 μm×3 μm. A writing voltage and a current value justbefore writing of the samples 5 to 8 are shown in FIG. 22. In FIG. 22,as each of the samples 5 to 8, a plurality of elements are manufacturedand measured under the same condition. The elements manufactured underthe same condition are represented by the same dots in the graph. InFIG. 22, the measurement data of the samples 5 to 8 is represented asfollows: the samples 5 are represented as black circles; the samples 6are represented as white circles; the samples 7 are represented as blacktriangles; and the samples 8 are represented as white triangles.

As shown in FIG. 22, the memory elements each having an organic compoundlayer including an insulator of the present invention (the samples 7 andthe samples 8) have a little variation in the writing voltage and thecurrent. Alternatively, in the memory elements each having a bufferlayer of a thin-film insulator between the first conductive layer andthe organic compound layer (the sample 5 and the sample 6), there aresome memory elements with high writing voltage.

When the memory element is manufactured under a bad film formingcondition, unusual element characteristics may be shown. By formingmemory elements by including an insulator in an organic compound layeras the present invention, a state of the organic compound layer(morphology) is stabilized, and uniformity of a film thickness can beimproved. Accordingly, the element characteristics are stabilizedwithout variation. Further, since the insulator and the organic compoundlayer are not required to be formed in a separation process, the processcan be simplified.

Subsequently, memory elements each having an organic compound layerincluding an insulator of the present invention (samples 9 to 11) aremanufactured, and a writing voltage and a current value just beforewriting are manufactured. As the samples, the sample 9 having a stackedlayer structure of a first conductive layer (a titanium film), anorganic compound (NPB) layer including an insulator (lithium fluoride)(a film thickness of 20 nm) (a volume ratio of lithium fluoride and NPBis 1:1), and a second conductive layer (an aluminum film) ismanufactured. Further, the sample 10 having a stacked layer structure ofa first conductive layer (a titanium film), an organic compound (NPB)layer including an insulator (calcium fluoride) (a film thickness of 20nm) (a volume ratio of calcium fluoride and NPB is 1:1), and a secondconductive layer (an aluminum film) is manufactured. Furthermore, thesample 11 having a stacked layer structure of a first conductive layer(a titanium film), an organic compound (TPAQn) layer including aninsulator (lithium fluoride) (a film thickness of 12 nm) (a volume ratioof lithium fluoride and TPAQn is 1:1), and a second conductive layer (analuminum film) is manufactured. The sample 10 in which an insulatinglayer in a thin film a state and the organic compound layer including aninsulator are stacked, is an example where the structure has aconcentration gradient of an insulator in a memory element.

A writing voltage and a current of the sample 9, the sample 10, and thesample 11 are respectively shown in FIG. 23A, FIG. 23B, and FIG. 24A. Asa writing method in this case, sweep measure by which a current value ofthe samples in each voltage is measured with increasing a voltage byevery 0.1 V from 0 V, is performed. As shown in FIGS. 23A and B, andFIG. 24, in the samples 9 to 11, writing current and voltagecharacteristics (I-V characteristics) of an element is stabilizedwithout variation, and conduct can be stabilized. Further, afterwriting, resistance is not remained in the memory elements, andresistance is almost disappeared.

A result is shown, in which writing is performed into a memory element(a sample 12) having a stacked layer structure of a first conductivelayer (a titanium film), an organic compound (TPAQn) layer including aninsulator (lithium fluoride) (a film thickness of 12 nm) (volume ratioof lithium fluoride and TPAQn is 1:1), and a second conductive layer (analuminum film), which uses the present invention having the similarstructure as the sample 11. As a writing method in this case, a pulsevoltage of 10 ms⁻¹ is applied to perform the writing into the memoryelement. FIG. 25 shows a number of writing elements with respect to eachwriting voltage. Writing of the memory element is performed in a rangeof a writing voltage of a certain degree. Therefore, it is confirmedthat the element using the present invention can be sufficiently usedfor a memory element.

In accordance with the above, it is possible that characteristics ofwriting voltage of the memory element or the like is stabilized withoutvariation by the memory element of the present invention, and thatnormal writing is performed in each element. Further, since a carrierinjecting property is improved by a tunnel current of a mixed layer ofan inorganic compound and an organic compound, an organic compound layercan be thickened. Therefore, a defect in which the memory element isshort-circuited in an initial state before having conductivity can beprevented. As a result, a memory device and a semiconductor device, eachof which has high reliability can be provided with high yield.

1. A semiconductor device comprising: a memory element comprising: anorganic compound layer comprising a plurality of insulating particlesover a first conductive layer; and a second conductive layer over theorganic compound layer, and wherein the plurality of insulatingparticles are dispersed in the organic compound layer.
 2. Asemiconductor device according to claim 1, wherein the first conductivelayer and the second conductive layer include an insulating particle. 3.A semiconductor device according to claim 1, wherein a film thickness ofthe organic compound layer comprising the plurality of insulatingparticles is changeable after writing by electric action of thesemiconductor device.
 4. A semiconductor device comprising: a memoryelement comprising: an organic compound layer including an insulatorover a first conductive layer; and a second conductive layer over theorganic compound layer including the insulator, wherein the organiccompound layer including the insulator has a concentration gradient ofthe insulator.
 5. A semiconductor device according to claim 4, wherein aconcentration of the insulator in the organic compound layer includingan insulator at an interface of the organic compound layer and the firstconductive layer is higher than that at an interface of the organiccompound layer including an insulator and the second conductive layer.6. A semiconductor device according to claim 4, wherein a concentrationof the insulator in the organic compound layer including an insulator atan interface of the organic compound layer including an insulator andthe second conductive layer is higher than that at an interface of theorganic compound layer including an insulator and the first conductivelayer.
 7. A semiconductor device according to claim 4, wherein aconcentration of the insulator in the organic compound layer includingan insulator at an interface of the organic compound layer including aninsulator and the first conductive layer and at an interface of theorganic compound layer including an insulator and the second conductivelayer is highest in the organic compound layer including an insulator.8. A semiconductor device according to claim 4, wherein the insulatorhas a particle shape.
 9. A semiconductor device according to claim 1 or4, wherein a part of the first conductive layer and the secondconductive layer contact each other after writing by adding electricaction of the semiconductor device.
 10. A semiconductor device accordingto claim 4, wherein a film thickness of the organic compound layerincluding the insulator is changed after writing by electric action ofthe semiconductor device.
 11. A semiconductor device according to claim4, wherein the first conductive layer and the second conductive layerinclude an insulator.